The Drosophila melanogaster sir2⁺ Gene Is Nonessential and Has Only Minor Effects on Position-Effect Variegation

Corresponding author: Stefan U. Åström, Wennergren Institute, Stockholm University, Arrhenius Laboratories E3, SE-106 91 Stockholm, Sweden., stefan.astrom{at}devbio.su.se (E-mail)

Communicating editor: K. V. ANDERSON

Five Drosophila melanogaster genes belong to the highly conserved sir2 family, which encodes NAD⁺-dependent protein deacetylases. Of these five, dsir2⁺ (CG5216) is most similar to the Saccharomyces cerevisiae SIR2 gene, which has profound effects on chromatin structure and life span. Four independent Drosophila strains were found with P-element insertions near the dsir2 transcriptional start site as well as extraneous linked recessive lethal mutations. Imprecise excision of one of these P elements (PlacW 07223) from a chromosome freed of extraneous lethal mutations produced dsir2¹⁷, a null intragenic deletion allele that generates no DSIR2 protein. Contrary to expectations from the report by Rosenberg and Parkhurst on their P-mobilization allele dSir2^ex10, homozygosity for dsir2¹⁷ had no apparent deleterious effects on viability, developmental rate, or sex ratio, and it fully complemented sir2^ex10. Moreover, through a genetic test, we ruled out the reported effect of dSir2^ex10 on Sex-lethal expression. We did observe a modest, strictly recessive suppression of white^m4 position-effect variegation and a shortening of life span in dsir2 homozygous mutants, suggesting that dsir2 has some functions in common with yeast SIR2.

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