An imprinting function of DNA polymerase alpha in establishment of mating type silencing in Schizosaccharomyces pombe

Ahmed, Shakil and Singh, Jagmohan (2001) An imprinting function of DNA polymerase alpha in establishment of mating type silencing in Schizosaccharomyces pombe. Current Science, 80. pp. 1337-1343.

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Abstract

Parental imprinting is a well-known phenomenon in higher eukaryotes. Similar epigenetic phenomena occur in budding yeast and fission yeast as represented by silencing, In Schizosaccharomyces pombe, the same genetic information is expressed at one locus mat1, but silenced at two other loci, mat2 and mat3 (and also the cases of centromere and telomere loci). Studies in both yeasts have suggested an integral role of DNA replication or passage through S phase in establishment of the silent state. Deletion of K region lying between the mat2 and mat3 loci establishes two alternative, stable epigenetic states of silencing, which are stably inherited during mitosis and meiosis, Recently, we have shown that in S, pombe the mating type silencing is abrogated at permissive temperature in a novel, dominant and temperature-sensitive mutant of DNA polymerase a. Here, we show that this mutant exhibits two alternative states, the repressed and the derepressed states, which are stably inherited during passage through mitosis. During meiosis, these alternate states segregate in a Mendelian fashion, indicating that these represent imprinted chromosomal mat loci. These alternate states are associated with different chromatin structures and in the derepressed state the chromodomain protein swi6 is delocalized from the mat loci. These results show that DNA polymerase Alpha, the enzyme required for lagging strand synthesis during DNA replication, plays a direct and integral role in establishing an imprinted chromatin structure by recruiting the heterochromatin-associated protein swi6, thus coupling DNA replication with establishment of silencing. We speculate that such a mechanism may be widely conserved among higher eukaryotes.

Item Type: Article
Additional Information: OPEN ACCESS
Subjects: Q Science > Q Science (General)
Depositing User: Dr. K.P.S.Sengar
Date Deposited: 03 Feb 2012 16:13
Last Modified: 07 Jan 2015 09:45
URI: http://crdd.osdd.net/open/id/eprint/871

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