The Mammalian SIR2α Protein Has a Role in Embryogenesis and Gametogenesis

Abstract

ABSTRACT The yeast Sir2p protein has an essential role in maintaining telomeric and mating type genes in their transcriptionally inactive state. Mammalian cells have a very large proportion of their genome inactive and also contain seven genes that have regions of homology with the yeast sir2 gene. One of these mammalian genes, sir2 α, is the presumptive mammalian homologue of the yeast sir2 gene. We set out to determine if sir2 α plays a role in mammalian gene silencing by creating a strain of mice carrying a null allele of sir2 α. Animals carrying two null alleles of sir2 α were smaller than normal at birth, and most died during the early postnatal period. In an outbred background, the sir2 α null animals often survived to adulthood, but both sexes were sterile. We found no evidence for failure of gene silencing in sir2 α null animals, suggesting that either SIR2 α has a different role in mammals than it does in Saccharomyces cerevisiae or that its role in gene silencing in confined to a small subset of mammalian genes. The phenotype of the sir2 α null animals suggests that the SIR2α protein is essential for normal embryogenesis and for normal reproduction in both sexes.