DNA double-strand breaks relieve USF-mediated repression of D?2 germline transcription in developing thymocytes.

ABSTRACT: Activation of germline promoters is central to V(D)J recombinational accessibility, driving chromatin remodeling, nucleosome repositioning, and transcriptional read-through of associated DNA. We have previously shown that of the two TCR? locus (Tcrb) D segments, D?1 is flanked by an upstream promoter that directs its transcription and recombinational accessibility. In contrast, transcription within the DJ?2 segment cluster is initially restricted to the J segments and only redirected upstream of D?2 after D-to-J joining. The repression of upstream promoter activity prior to Tcrb assembly correlates with evidence that suggests DJ?2 recombination is less efficient than that of DJ?1. Because inefficient DJ?2 assembly offers the potential for V-to-DJ?2 recombination to rescue frameshifted V-to-DJ?1 joints, we wished to determine how D?2 promoter activity is modulated upon Tcrb recombination. In this study, we show that repression of the otherwise transcriptionally primed 5'D?2 promoter requires binding of upstream stimulatory factor (USF)-1 to a noncanonical E-box within the D?2 12-recombination signal sequence spacer prior to Tcrb recombination. USF binding is lost from both rearranged and germline D?2 sites in DNA-dependent protein kinase, catalytic subunit-competent thymocytes. Finally, genotoxic dsDNA breaks lead to rapid loss of USF binding and gain of transcriptionally primed 5'D?2 promoter activity in a DNA-dependent protein kinase, catalytic subunit-dependent manner. Together, these data suggest a mechanism by which V(D)J recombination may feed back to regulate local D?2 recombinational accessibility during thymocyte development.

SUBMITTER: Stone JL 

PROVIDER: S-EPMC3288432 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature