Host defenses to parasitic sequences and the evolution of epigenetic control mechanisms

Genetica

Volumn 107, Issue 1-3, 1999, Pages 271-287

  Matzke, M A ^a   Mette, M F ^a   Aufsatz, W ^a   Jakowitsch, J ^a   Matzke, A J M ^a  

^a ERICH SCHMID INSTITUTE OF MATERIALS SCIENCE   (Austria)

Author keywords

DNA methylation; Epigenetic silencing; Genome evolution; Polyploidy; Transgenic plants; Transposable elements; Viroids

Indexed keywords

EUKARYOTA; ILEX COOKII; RNA VIRUSES; VERTEBRATA; VIROIDS;

ARTICLE; DNA METHYLATION; GENE DOSAGE; GENE SILENCING; GENETIC TRANSCRIPTION; MOLECULAR EVOLUTION; PROMOTER REGION; TRANSGENE;

DNA METHYLATION; EVOLUTION, MOLECULAR; GENE DOSAGE; GENE SILENCING; PROMOTER REGIONS (GENETICS); TRANSCRIPTION, GENETIC; TRANSGENES;

EID: 0033291381     PISSN: 00166707     EISSN: None     Source Type: Journal    
DOI: 10.1023/a:1003921710672     Document Type: Article

References (130)

1. Agrawal, A., Q.M. Eastman & D.G. Schatz, 1998. Transposition mediated by RAG1 and RAG2 and its implications for the evolution of the immune system. Nature 394: 744-751.
2. Anandalakshmi, R., G. Pruss, X. Ge, R. Marathe, A.C. Mallory, T.H. Smith & V.B. Vance, 1998. A viral suppressor of gene silencing in plants. Proc. Natl. Acad. Sci. USA 95: 13079-13084.
3. Avramova, Z., A. Tikhonov, M. Chen & J.L. Bennetzen, 1998. Matrix attachment regions and structural colinearity in the genomes of two grass species. Nucl. Acids Res. 26: 761-777.
4. Barlow, D.P., 1993. Methylation and imprinting: from host defense to gene regulation? Science 260: 309-310.
5. Béclin, C., R. Berthomé, J.-C. Palauqui, M. Tepfer & H. Vaucheret, 1998. Infection of tobacco or Arabidopsis plants by CMV counteracts systemic post-transcriptional silencing of nonviral (trans)genes. Virology 252: 313-317.
6. Bender, J. & G.R. Fink, 1995. Epigenetic control of an endogenous gene family is revealed by a novel blue fluorescent mutant of Arabidopsis. Cell 83: 725-734.
7. Bennett, S.T., A.J. Wilson, L. Esposito, et al., 1997. Insulin VNTR allele-specific effect in type 1 diabetes depends on identity of untransmitted paternal allele. Nat. Genet. 17: 350-352.
8. Bestor, T. & B. Tycko, 1996. Creation of genomic methylation patterns. Nat. Genet. 12: 363-367.
9. Bestor, T., A. Laudano, R. Mattaliano & V. Ingram, 1988. Cloning and sequencing of a cDNA encoding DNA methyltransferase of mouse cells. J. Mol. Biol. 203: 971-983.
10. Bestor, T.H., 1990. DNA methylation: evolution of a bacterial immune function into a regulator of gene expression and genome structure in higher eukaryotes. Phil. Trans. R. Soc. Lond. B 326: 179-187.
11. Bestor, T.H., 1998. The host defense function of genomic methylation patterns, pp. 187-199 in Epigenetics edited by D.J. Chadwick and A.P. Wolffe, Novartis Foundation Symposium vol. 214, Wiley, Chichester.
12. Birchler, J.A., M. Pal-Bhadra & U. Bhadra, 1999. Less from more: cosuppression of transposable elements. Natl. Genet. 21: 148-149.
13. Bird, A., 1997. Does DNA methylation control transposition of selfish elements in the germline? Trends Genet. 13: 469-470.
14. Bollman, J., R. Carpenter & E.S. Coen, 1991. Allelic interactions at the nivea locus of Antirrhinum. Plant Cell 3: 1327-1336.
15. Brigneti, G., O. Voinnet, W.-X. Li, L.-H. Ji, S.-W. Ding & D.C. Baulcombe, 1998. Viral pathogenicity determinants are suppressors of transgene silencing in Nicotiana benthamiana. EMBO J. 17: 6739-6746.
16. Britten, R.J., 1996 DNA sequence insertion and evolutionary variation in gene regulation. Proc. Natl. Acad. Sci. USA 93: 9374-9377.
17. Britten, R.J., 1997. Mobile elements inserted in the distant past have taken on important functions. Gene 205: 177-182.
18. Casacuberta, E., J.M. Casacuberta, P. Puigdomènech & A. Monfort, 1998. Presence of miniature inverted-repeat transposable elements (MITES) in the genome of Arabidopsis thaliana: characterisation of the Emigrant family of elements. Plant J. 16: 79-85.
19. Chaboissier, M.-C., A. Bucheton & D.J. Finnegan, 1998. Copy number control of a transposable element, the I factor, a LINE-like element in Drosophila. Proc. Natl. Acad. Sci. USA 95: 11781-11785.
20. Chadwick, D.J. & A.P. Wolffe, 1998. Novartis Foundation Symposium Vol 214, Epigenetics, Wiley, Chichester.
21. Cogoni C. & G. Macino, 1997. Conservation of transgene-induced post-transcriptional gene silencing in plants and fungi. Trends Plant Sci. 2: 438-443.
22. Cogoni, C. & G. Macino, 1997. Isolation of quelling-defecive (qde) mutants imparied in posttranscriptional transgene-induced gene silencing in Neurospora crassa. Proc. Natl. Acad. Sci. USA 94: 10233-10238.
23. Cogoni, C. & G. Macino, 1999. Gene silencing in Neurospora requires a protein homologous to RNA-dependent RNA polymerase. Nature 399: 166-169.
24. Cogoni, C., J. Irelan, M. Schumacher, T. Schmidhauser, E. Selker & G. Macino, 1996. Transgene silencing of the al-1 gene in vegetative cells of Neurospora is mediated by a cytoplasmic effector and does not depend on DNA-DNA interactions or DNA methylation. EMBO J. 15: 3153-3163.
25. Colot, V. & J.-L. Rossignol, 1999. Eukaryotic DNA methylation as an evolutionary device. BioEssays 21: 402-411.
26. Colot, V., L. Maloisel & J.-L. Rossignol, 1997. Interchromosomal transfer of epigenetic states in Ascobolus: transfer of DNA methylation is mechanistically related to homologous recombination. Cell 86: 855-864.
27. Coppin-Raynal, E., M. Picard & S. Arnaise, 1989. Transformation by integration in Podospora anserina. Mol. Gen. Genet. 219: 270-276.
28. Csink, A.K. & S. Henikoff, 1996. Genetic modification of heterochromatic association and nuclear organization in Drosophila. Nature 381: 529-531.
29. Cubas, P., C. Vincent & E. Coen, 1999. An epigenetic mutation responsible for natural variation in floral symmetry. Nature 401: 157-161.
30. DeBerardinis, R.J., J.L. Goodier, E.M. Ostertag & H.H. Kazazian, 1998. Rapid amplification of a retrotransposon subfamily is evolving the mouse genome. Nat. Genet. 20: 288-290.
31. Dorer, D.R. & S. Henikoff, 1994. Expansions of transgene repeats cause heterochromatin formation and gene silencing in Drosophila. Cell 77: 993-1002.
32. Dorer, D.R. & S. Henikoff, 1997. Transgene repeat arrays interact with distant heterochromatin and cause silencing in cis and in trans. Genetics 147: 1181-1190.
33. Dupressoir, A. & T. Heidmann, 1996. Germ line-specific expression of intracisternal A-particle retrotransposons in transgenic mice. Mol. Cell Biol. 16: 4495-4503.
34. Elmayan, T., S. Balzergue, F. Béon, V. Bourdon, J. Daubremet, Y. Guénet, P. Mourrain, J.-C. Palauqui, S. Vernhettes, T. Vialle, K. Wostrikoff & H. Vaucheret, 1998. Arabidopsis mutants impaired in cosuppression. Plant Cell 10: 1747-1757.
35. English, J.J., E. Mueller & D.C. Baulcombe, 1996. Suppression of virus accumulation in transgenic plants exhibiting silencing of nuclear genes. Plant Cell 8: 179-188.
36. Finnegan, E.J., R.K. Genger, W.J. Peacock & E.S Dennis, 1998. DNA methylation in plants. Annu. Rev. Plant Physiol. Plant Mol. Biol. 49: 223-248.
37. Fire, A., 1999. RNA-triggered gene silencing. Trends Genet. 15: 358-363.
38. Gallardo, M.H., J.W. Bickham, R.L. Honeycutt, R.A. Ojeda & N. Köhler, 1999. Discovery of tetraploidy in a mammal. Nature 401: 341.
39. Goodwin, J., K. Chapman, S. Swaney, T.D. Parks, E.A. Wernsman & W.G. Dougherty, 1996. Genetic and biochemical dissection of transgenic RNA-mediated virus resistance. Plant Cell 8: 95-105.
40. Gonzalgo, M.L. & P.A. Jones, 1997. Mutagenic and epigenetic effects of DNA methylation. Mut. Res. 386: 107-118.
41. Hendrich, B., U. Hardeland, H.-H. Ng, J. Jiricny & A. Bird, 1999. The thymine glycosylase MBD4 can bind to the product of deamination at methylated CpG sites. Nature 401: 301-304.
42. Henikoff, S. & L. Comai, 1998. A DNA methyltransferase homolog with a chromodomain exists in multiple polymorphic forms in Arabidopsis. Genetics 149: 307-318.
43. Henikoff, S. & M.A. Matzke, 1997. Exploring and explaining epigenetic effects. Trends Genet. 13: 293-341.
44. Hiom, K., M. Melek & M. Gellert, 1998. DNA transposition by the RAG1 and RAG2 proteins: possible source of oncogenic translocations. Cell 94: 63-470.
45. Hollick, J.B., J.E. Dorweiler & V.L. Chandler, 1997. Paramutation & related allelic interactions. Trends Genet. 13: 293-341.
46. Horsthemke, B., B. Dittrich & K. Buiting, 1997. Imprinting mutations on human chromosome 15. Human Mutation 10: 329-337.
47. Jacobsen, S.E. & E.M. Meyerowitz, 1997. Hypermethylated SUPERMAN epigenetic alleles in Arabidopsis. Science 277: 1100-1103.
48. Jacobsen, S.E., 1999. Gene silencing: maintaining methylation patterns. Curr. Biol. 9: R617-R619.
49. Jakowitsch, J., I. Papp, E.A. Moscone, J. van der Winden, M. Matzke & A.J.M. Matzke, 1999. Molecular and cytogenetic characterization of a transgene locus that induces silencing and methylation of homologous promoters in trans. Plant J. 17: 131-140.
50. Jeddeloh, J.A., T.L. Stokes & E.J. Richards, 1999. Maintenance of genomic methylation requires a SWI2/SNF2-like protein. Nat. Genet. 22: 94-96.
51. Jensen, S., M.-P. Gassama & T. Heidmann, 1999. Taming of transposable elements by homology-dependent gene silencing. Nat. Genet. 21: 209-212.
52. Jones, A.L., C.L. Thomas & A.J. Maule, 1998. De novo methylation and cosuppression induced by a cytoplasmically replicating plant RNA virus. EMBO J. 17: 6385-6393.
53. Jones, P.L., G. Veenstra, P.A. Wade, D. Vermaak, S.U. Kass, N. Landsberger, J. Strouboulis & A.P. Wolffe, 1998. Methylated DNA & MeCP2 recruit histone deacetylase to repress transcription. Nat. Genet. 19: 187-191.
54. Jorgensen, R.A., R.G. Atkinson, R.L.S. Forster & W.J. Lucas, 1998. An RNA-based information superhighway in plants. Science 279: 1486-1487.
55. Kasschau, K.D. & J.C. Carrington, 1998. A counterdefensive strategy of plant viruses: suppression of post-transcriptional gene silencing. Cell 95: 461-470.
56. Kermicle, J.L., W.B. Eggleston & M. Alleman, 1995. Organization of paramutagenicity in R-stippled maize. Genetics 141: 361-372.
57. Kidwell, M. & D. Lisch, 1997. Transposable elements as sources of variation in animals and plants. Proc. Natl. Acad. Sci. USA 94: 7704-7711.
58. Kiefer, M.C., R.A. Owens & T.O. Diener, 1983. Structural similarities between viroids and transposable genetic elements. Proc. Natl. Acad. Sci. USA 80: 6234-6238.
59. Kooter, J., M.A. Matzke & P. Meyer, 1999. Listening to the silent genes: transgene silencing, gene regulation and pathogen control. Trends Plant Sci. 4: 340-347.
60. Lafontaine, D.L. & D. Tollervey, 1998. Birth of the snoRNPs: the evolution of the modification-guide snoRNAs. Trends Biochem. Sci. 23: 383-388.
61. Lee, J.T., L.S. Davidow & D. Warshawsky, 1999. Tsix, a gene antisense to Xist at the X-inactivation center. Nat. Genet. 21: 400-404.
62. Levis, R., R. Ganesan, K. Houtchens, L.A. Tolar & F.-M. Sheen, 1993. Transposons in place of telomeric repeats at a Drosophila telomere. Cell 75: 1083-1093.
63. Li, E., T.H. Bestor & R. Jaenisch, 1992. Targeted mutation of the DNA methyltransferase gene results in embryonic lethality. Cell 69: 915-926.
64. Li, H.-W., A.P. Lucy, H.-S. Guo, W.-X. Li, L.-H. Ji, S.-M. Wong & S.-W. Ding, 1999. Strong host resistance targeted against a viral suppressor of the plant gene silencing defence mechanisms. EMBO J. 18: 2683-2691.
65. Lindbo, J.A., L. Silva-Rosales, W.M. Proebsting & W.G. Dougherty, 1993. Induction of a highly specific antiviral state in transgenic plants: implications for regulation of gene expression and virus resistance. Plant Cell 5: 1749-1759.
66. Luff, B., L. Pawlowski & J. Bender, 1999. An inverted repeat triggers cytosine methylation of identical sequences in Arabidopsis. Mol. Cell 3: 505-511.
67. Lyon, M., 1998. X-chromosome inactivation: a repeat hypothesis. Cytogenet. Cell Genet. 80: 133-137.
68. Malagnac, F., F. Wendel, C. Goyon, G. Faugeron, D. Zickler, J.-L. Rossignol, M. Noyer-Weidner, T Trautner & J. Walter, 1997. A gene essential for de novo methylation and development in Ascobolus reveals a novel type of eukaryotic DNA methyltransferase structure. Cell 91: 1-20.
69. Martienssen, R., 1996. Epigenetic phenomena: paramutation and gene silencing in plants. Curr. Biol. 6: 810-813.
70. Masterson, J.S., 1994. Stomatal size in fossil plants: evidence for polyploidy in the majority of angiosperms. Science 264: 421-424.
71. Matzke, A.J.M., F. Neuhuber, Y-D. Park, P. Ambros & M.A. Matzke, 1994. Homology-dependent gene silencing in transgenic plants: epistatic silencing loci contain multiple copies of methylated transgenes. Mol. Gen. Genet. 244: 219-229.
72. Matzke, A.J.M. & M.A. Matzke, 1998a. Position effects and epigenetic silencing of plant transgenes. Curr. Opin. Plant Biol. 1: 142-148.
73. Matzke, M.A. & A.J.M. Matzke, 1998b. Epigenetic silencing of plant transgenes as a consequence of distinct cellular defense responses. Cell Mol. Life Sci. 54: 94-103.
74. Matzke, M.A. & A.J.M. Matzke, 1998c. Gene silencing in plants: relevance for genome evolution and the acquisition of genomic methylation patterns, pp.168-186 in Epigenetics edited by D.J. Chadwick and A.P. Wolffe, Novartis Foundation Symposium vol 214, Wiley Chichester.
75. Matzke, M.A., A.J.M. Matzke & W. Eggleston, 1996. Transgene silencing and paramutation: a common response to invasive DNA? Trends Plant Sci. 1: 382-388.
76. Matzke, M.A., M.P. Primig, J. Trnovsky & A.J.M. Matzke, 1989. Reversible methylation and inactivation of marker genes in sequentially transformed tobacco plants. EMBO J. 8: 643-649.
77. McDonald, J.F., 1998. Transposable elements, gene silencing and macroevolution. Trends Ecol. Evol. 13: 94-95.
78. McDonald, J.F., 1993. Evolution and consequences of transposable elements. Curr. Opin. Genet. Devel. 3: 855-864.
79. McDonald, J.F., 1995. Transposable elements: possible catalysts of organismic evolution. Trends Ecol. Evol. 10: 123-126.
80. Melquist, S., B. Luff & J. Bender, 1999. Arabidopsis PAI gene arrangements, cytosine methylation and expression. Genetics 153: 401-413.
81. Mette, M.F., J. van der Winden, M.A. Matzke & A.J.M. Matzke, 1999. Production of aberrant promoter transcripts contributes to methylation and silencing of unlinked homologous promoters in trans. EMBO J. 18: 241-248.
82. Meyer, P., I. Heidmann & I. Niedenhof, 1993. Differences in DNA methylation are associated with a paramutation phenomenon in transgenic petunia. Plant J. 4: 89-100.
83. Mittelsten Scheid, O., K. Afsar & J. Paszkowski, 1998. Release of epigenetic silencing by trans-acting mutations in Arabidopsis. Proc. Natl. Acad. Sci. USA 95: 632-637.
84. Nan, X., H.-H. Ng, C.A. Johnson, C.D. Laherty, B.M. Turner, R.N. Eisenman & A. Bird, 1998. Transcriptional repression by the methyl-CpG-binding protein MeCP2 involves a histone deacetylase complex. Nature 393: 386-389.
85. Napoli, C., C. Lemieux & R. Jorgensen, 1990. Introduction of a chimeric chalcone synthase gene into petunia results in reversible cosuppression of homologous genes in trans. Plant Cell 2: 279-289.
86. Ng, H.-H., Y. Zhang, B. Hendrich, C.A. Johnson, B.M. Turner, H. Erdjument-Bromage, P. Tempst, D. Reinberg & A. Bird, 1999. MBD2 is a transcriptional repressor belonging to the MeCP1 histone deacetylase complex. Nat. Genet. 23: 58-61.
87. O'Neill, R.J., M.J. O'Neill & J.A. Graves, 1998. Undermethylation associated with retroelement activation and chromosome remodeling in an interspecific mammalian hybrid. Nature 393: 68-72.
88. Palauqui, J.-C., T. Elmayan, J.-M. Pollien & H. Vaucheret, 1997. Systemic acquired silencing: transgene-specific post-transcriptional silencing is transmitted by grafting from silenced stocks to non-silenced scions. EMBO J. 16: 4738-4745.
89. Pal-Bhadra, M., U. Bhadra & J.A. Birchler, 1997. Cosuppression in Drosophila: gene silencing of Alcohol dehydrogenase by white-Adh transgenes is Polycomb dependent. Cell 90: 479-490.
90. Park, Y.-D., I. Papp, E.A. Moscone, V.A. Iglesias, H. Vaucheret, A.J.M. Matzke & M.A. Matzke, 1996. Gene silencing mediated by promoter homology occurs at the level transcription and results in meiotically heritable alterations in methylation and gene activity. Plant J. 9: 183-194.
91. Pélissier, T., S. Tutois, J.M. Deragon, S. Tourmente, S. Genestier & G. Picard, 1995. Athila, a new retroelement from Ambidopsis thaliana. Plant Mol. Biol. 29: 441-452.
92. Ratcliff, F., B.D. Harrison & D.C. Baulcombe, 1997. A similarity between viral defense and gene silencing in plants. Science 276: 1558-1560.
93. Regev, A., M. Lamb & E. Jablonka, 1998. The role of DNA methylation in invertebrates: developmental regulation or genome defense? Mol. Biol. Evol. 15: 880-891.
94. Richards, E., 1997. DNA methylation and plant development. Trends Genet. 13: 319-322.
95. Rossignol, J.-L. & G. Faugeron, 1994. Gene inactivation triggered by recognition between DNA repeats. Experientia 50: 307-317.
96. Russo, V.A., R. Martienssen & A. Riggs, 1996. Epigenetic Mechanisms of Gene Regulation, Cold Spring Harbor Press, New York.
97. SanMiguel, P., B.S. Gaut, A. Tikhonov, Y. Nakajima & J.L. Bennetzen, 1998. The paleontology of intergenic retrotransposons of maize. Nat. Genet. 20: 43-45.
98. SanMiguel, P., A. Tikhonov, Y. Jin, N. Motchoulskaia, D. Zakharov, A. Melake-Berhan, P.S. Springer, K.J. Edwards, M. Lee, Z. Avramova & J.L. Bennetzen, 1996. Nested retrotransposons in the intergenic regions of the maize genome. Science 274: 765-768.
99. Schiebel, W., T. Pélissier, L. Riedel, S. Thalmeir, R. Schiebel, D. Kempe, F. Lottspeich, H. Sänger & M. Wassenegger, 1998. Isolation of an RNA-directed RNA polymerase-specific cDNA clone from tomato. Plant Cell 10: 2087-2101.
100. Selker, E.U., 1990. Premeiotic instability of repeated sequences in Neurospora. Annu. Rev. Genet. 24: 579-614.
101. Selker, E.U., 1997. Epigenetic phenomena in filamentous fungi: useful paradigms or repeat-induced confusion? Trends Genet. 13: 296-310.
102. Selker, E.U., 1999. Repeats that count. Cell 97: 157-160.
103. Sheen, F.-M. & R.W. Levis, 1994. Transposition of the LINE-like retrotransposon TART to Drosophila chromosome termini. Proc. Natl. Acad. Sci. USA 91: 12510-12514.
104. Simmen, M.W., S. Leitgeb, J. Charlton, S.J.M. Jones, B.R. Harris, V.H. Clark & A. Bird, 1999. Nonmethylated transposable elements and methylated genes in a chordate genome. Science 283: 1164-1167.
105. Singer, M., B. Marcotte & E. Selker, 1995. DNA methylation associated with repeat-induced point mutation in Neurospom crassa. Mol. Cell Biol. 15: 5586-5597.
106. Smith, C.J.S., C.F. Watson, C.R. Bird, J. Ray, W. Schuch & D. Grierson, 1990. Expression of a truncated tomato polygalacturonase gene inhibits expression of the endogenous gene in transgenic plants. Mol. Gen. Genet. 224: 447-481.
107. Smith, H., 1999. Interfering with viral infection: plants do it too. Plant Cell 11: 1191-1193.
108. Smith, C.M. & J.A. Steitz, 1997. Sno storm in the nucleolus: new roles for myriad small RNPs. Cell 89: 669-672.
109. Spring, J., 1997. Vertebrate evolution by interspecific hybridization - are we polyploid? FEBS Lett. 400: 2-8.
110. Stam, M., A. Viterbo, J.N.M. Mol & J.M. Kooter, 1998. Position-dependent methylation and transcriptional silencing of transgenes in inverted T-DNA repeats: implications for posttranscriptional silencing of homologous host genes in plants. Mol. Cell Biol. 18: 6165-6177.
111. Stinard, P.S., D.S. Robertson & P.S. Schnable, 1993. Genetic isolation, cloning, and analysis of a Mutator-induced, dominant antimorph of the maize amylose extender1 locus. Plant Cell 5: 1555-1566.
112. Todd, J.J. & L.O. Vodkin, 1996. Duplications that suppress and deletions that restore expression from a chalcone synthase multigene family. Plant Cell 8: 687-699.
113. Turker, M.S. & T.H. Bestor, 1997. Formation of methylation patterns in the mammalian genome. Mut. Res. 386: 119-130.
114. van Blokland, R., N. van der Geest, J.N.M. Mol & J.M. Kooter, 1994. Transgene-mediated suppression of chalcone synthase expression in Petunia hybrida results from an increase in RNA turnover. Plant J. 6: 861-877.
115. van der Krol, A.R., L.A. Mur, M. Beld, J.N.M. Mol & A.R. Stuitje, 1990. Flavonoid genes in petunia: addition of a limited number of gene copies may lead to a suppression of gene expression. Plant Cell 2: 291-299.
116. Van Houdt, H., I. Ingelbrecht, M. Van Montagu & A. Depicker, 1997. Post-transcriptional silencing of aneomycin phosphotransferase II transgene correlates with the accumulation of unpro-ductive RNAs and with increased cytosine methylation of 3′ flanking regions. Plant J. 12: 379-392.
117. Vaucheret, H., 1993. Identification of a general silencer for 19S and 35S promoters in a transgenic tobacco plants: 90 bp of homology in the promoter region are sufficient for trans-inactivation. C.R. Acad. Sci. Paris 316: 1471-1483.
118. Voinnet, O. & D.C. Baulcombe, 1997. Systemic signaling in gene silencing. Nature 389: 553.
119. Wade, P.A., A. Gegonne, P.L. Jones, E. Ballestar, F. Aubry & A.P. Wolffe, 1999. Mi-2 complex couples DNA methylation to chromatin remodeling and histone deacetylation. Nat. Genet. 23: 62-66.
120. Walker, E.L., 1998. Paramutation of the r1 locus of maize is associated with increased cytosine methylation. Genetics 148: 1973-1981.
121. Walsh, C.P. & T.H. Bestor, 1998. Transcription of IAP endogenous retroviruses is constrained by cytosine methylation. Nat. Genet. 20: 116-117.
122. Walsh, C.P. & T.H. Bestor, 1999. Cytosine methylation and mammalian development. Genes Devel. 13: 26-34.
123. Wassenegger, M. & T. Pélissier, 1998. A model for RNA-mediated gene silencing in higher plants. Plant Mol. Biol. 37: 349-362.
124. Wassenegger, M. & T. Pélissier, 1999. Signaling in gene silencing. Trends Plant Sci. 4: 207-209.
125. Wassenegger, M., S. Himes, L. Riedel & H. Sänger, 1994. RNA-directed de novo methylation of genomic sequences in plants. Cell 76: 567-576.
126. Waterhouse, P.M., H.W. Graham & M.B. Wang, 1998. Virus resistance and gene silencing in plants can be induced by simultaneous expression of sense and antisense RNA. Proc. Natl. Acad. Sci. USA 95: 13959-13964.
127. Wessler, S., 1998. Transposable elements associated with normal plant genes. Physiologia Plantarum 103: 581-586.
128. Wolffe, A. & M.A. Matzke, 1999. Epigenetics: regulation through repression. Science, 286: 481-486.
129. Wu, C.-T. & J.R. Morris, 1999. Transvection and other homology effects. Curr. Opin. Genet. Dev. 9: 237-246.
130. Yoder, J. A., C. Walsh & T.H. Bestor, 1997. Cytosine methylation and the ecology of intragenomic parasites. Trends Genet. 13: 335-339.