ADrosophilagene structurally and functionally homologous to the mammalian 70-kDa S6 kinase gene

Abstract
CDNAs encoding theDrosophila70-kDa S6 kinase (S6K) were isolated by low-stringency hybridization with mammalian p70S6kprobes. Conceptual translation ofS6kcDNA sequences yields a product containing all of the canonical features typical of serine/threonine kinases and has 78% amino acid identity in the catalytic domain with the human p70S6khomologue. TheS6kgene, located at polytene chromosome site 65D, gives rise to two predominant transcripts of 3.0 and 5.0 kb and at least two smaller transcripts (RpS6air8) mutant animals express higher levels of the smallerS6ktranscripts, suggesting tissue- or genotype-specific differences in the regulation of theS6kgene.DrosophilaS6K expressed in COS or NIH 3T3 cells phosphorylates mammalian RPS6 in a mitogen-dependent wortmannin- and rapamycin-sensitive manner, suggesting that its regulation is similiar to mammalian p70S6k.