Naresh, Alpana and Saini, Sharanjot and Singh, Jagmohan (2003) Identification of Uhp1, a ubiquitinated histone-like protein, as a target/mediator of Rhp6 in mating-type silencing in fission yeast. The Journal of biological chemistry, 278 (11). pp. 9185-94. ISSN 0021-9258

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Abstract

Mating-type silencing in Schizosaccharomyces pombe is brought about by cooperative interactions between cis-acting DNA sequences flanking mat2P and mat3M and the trans-acting factors, namely Swi6, Clr1-Clr4, Clr6, and Rik1. In addition, DNA repair gene rhp6, which plays a role in post-replication DNA repair and ubiquitination of proteins including histones, is also involved in silencing, albeit in a unique way; its effect on silencing and chromatin structure of the donor loci is dependent on their switching competence. Earlier, we hypothesized the existence of a mediator of Rhp6 that plays a role in reestablishment of the chromatin structure coincidentally with DNA replication associated with mating-type switching. Here we report the identification of a 22-kDa protein as an in vivo target and mediator of Rhp6 in mating-type silencing. The level of this protein is greatly elevated in sng1-1/rhp6(-) mutant and rhp6Delta as compared with wild type strain. Both the deletion and overexpression of the gene encoding this protein elicit switching-dependent loss of silencing. Furthermore, the 22-kDa protein undergoes Rhp6-dependent multiubiquitination and associates with mat2 locus during S phase in wild type cells. Interestingly, it contains a histone-fold motif similar to that of histone H2A, and like histone H2A, it interacts strongly with histone H2B in vitro. These results indicate that the 22-kDa protein, renamed as the ubiquitinated histone-like protein Uhp1, is an in vivo target/mediator of Rhp6 in silencing. Thus, regulation of association of Uhp1 with chromatin and ubiquitination followed by degradation may play a role in reestablishment of inactive chromatin structure at the silent mating-type loci.

Item Type:	Article
Additional Information:	Copyright of this article belongs to ASBMB.
Subjects:	Q Science > QD Chemistry
Depositing User:	Dr. K.P.S.Sengar
Date Deposited:	05 Jan 2012 15:06
Last Modified:	05 Jan 2012 15:06
URI:	http://crdd.osdd.net/open/id/eprint/255

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