The assembly and maintenance of heterochromatin initiated by transgene repeats are independent of the RNA interference pathway in mammalian cells

Autor: Tokuko Haraguchi, Fangwei Wang, Toshiro Tsukamoto, Naoki Koyama, Hiroko Nishida, Walter Reith
Jazyk: angličtina
Rok vydání: 2006
Předmět:
Ribonuclease III
Euchromatin
Transcription
Genetic
Chromosomal Proteins
Non-Histone
ddc:616.07
RNA interference
Heterochromatin
Cricetinae
Transgenes
RNA
Small Interfering
Promoter Regions
Genetic
Cells
Cultured
Chromatin Assembly and Disassembly/ genetics
Articles
Up-Regulation
Chromatin
CpG Islands/genetics
Protein Transport
Tandem Repeat Sequences
DNA methylation
RNA Interference
Tandem Repeat Sequences/ genetics
Lysine/metabolism
Transgene
Green Fluorescent Proteins
Methyltransferases/metabolism
Biology
Chromosomal Proteins
Non-Histone/genetics
Up-Regulation/genetics
Animals
Humans
Gene Silencing
Molecular Biology
Green Fluorescent Proteins/metabolism
Ribonuclease III/deficiency
Lysine
Repressor Proteins/metabolism
fungi
Methyltransferases
Cell Biology
DNA Methylation
Chromatin Assembly and Disassembly
Molecular biology
Promoter Regions
Genetic/genetics
Repressor Proteins
Transgenes/ genetics
Chromobox Protein Homolog 5
Heterochromatin/ genetics
biology.protein
CpG Islands
Heterochromatin protein 1
Euchromatin/genetics
5' Untranslated Regions
Dicer
Zdroj: Molecular and Cellular Biology, Vol. 26, No 11 (2006) pp. 4028-4040
ISSN: 0270-7306
Popis: A role for the RNA interference (RNAi) pathway in the establishment of heterochromatin is now well accepted for various organisms. Less is known about its relevance and precise role in mammalian cells. We previously showed that tandem insertion of a 1,000-copy inducible transgene into the genome of baby hamster kidney (BHK) cells initiated the formation of an extremely condensed chromatin locus. Here, we characterized the inactive transgenic locus as heterochromatin, since it was associated with heterochromatin protein 1 (HP1), histone H3 trimethylated at lysine 9, and cytosine methylation in CpG dinucleotides. Northern blot analysis did not detect any transgene-derived small RNAs. RNAi-mediated Dicer knockdown did not disrupt the heterochromatic transgenic locus or up-regulate transgene expression. Moreover, neither Dicer knockdown nor overexpression of transgene-directed small interfering RNAs altered the bidirectional transition of the transgenic locus between the heterochromatic and euchromatic states. Interestingly, tethering of HP1 to the transgenic locus effectively induced transgene silencing and chromatin condensation in a Dicer-independent manner, suggesting a role for HP1 in maintaining the heterochromatic locus. Our results suggest that the RNAi pathway is not required for the assembly and maintenance of noncentromeric heterochromatin initiated by tandem transgene repeats in mammalian cells.
Databáze: OpenAIRE
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