Cho DH, Thienes CP, Mahoney SE, Analau E, Filippova GN, Tapscott SJ. Antisense Transcription and Heterochromatin at the DM1 CTG Repeats Are Constrained by CTCF.
Mol Cell 2005;
20:483-9. [PMID:
16285929 DOI:
10.1016/j.molcel.2005.09.002]
[Citation(s) in RCA: 222] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2005] [Revised: 08/17/2005] [Accepted: 09/02/2005] [Indexed: 11/30/2022]
Abstract
Prior studies of the DM1 locus have shown that the CTG repeats are a component of a CTCF-dependent insulator element and that repeat expansion results in conversion of the region to heterochromatin. We now show that the DM1 insulator is maintained in a local heterochromatin context: an antisense transcript emanating from the adjacent SIX5 regulatory region extends into the insulator element and is converted into 21 nucleotide (nt) fragments with associated regional histone H3 lysine 9 (H3-K9) methylation and HP1gamma recruitment that is embedded within a region of euchromatin-associated H3 lysine 4 (H3-K4) methylation. CTCF restricts the extent of the antisense RNA at the wild-type (wt) DM1 locus and constrains the H3-K9 methylation to the nucleosome associated with the CTG repeat, whereas the expanded allele in congenital DM1 is associated with loss of CTCF binding, spread of heterochromatin, and regional CpG methylation.
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