No abstract

The completed fruit fly genome was found to contain up to 15 putative UDP-N-acetyl-␣-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-transferase) genes. Phylogenetic analysis of the putative catalytic domains of the large GalNAc-transferase enzyme families of Drosophila melanogaster (13 available), Caenorhabditis elegans (9 genes), and mammals (12 genes) indicated that distinct subfamilies of orthologous genes are conserved in each species. In support of this hypothesis, we provide evidence that distinctive functional properties of Drosophila and human GalNAc-transferase isoforms were exhibited by evolutionarily conserved members of two subfamilies (dGalNAc-T1 (l(2)35Aa) and GalNAc-T11; dGalNAc-T2 (CG6394) and GalNAc-T7). dGalNAc-T1 and novel human GalNAc-T11 were shown to encode functional GalNActransferases with the same polypeptide acceptor substrate specificity, and dGalNAc-T2 was shown to encode a GalNAc-transferase with similar GalNAc glycopeptide substrate specificity as GalNAc-T7. Previous data suggested that the putative GalNAc-transferase encoded by l(2)35Aa had a lethal phenotype (Flores, C., and Engels, W. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 2964-2969), and this was substantiated by sequencing of three lethal alleles l(2)35Aa HG8

Translational silencing phenomena during spermatogenesis in the two model systems Drosophila and mouse are reviewed. Cis-acting sequences were identified in both species that are necessary for translational repression. While in Drosophila these elements so far have only been found in the 5' untranslated region (5' UTR), in the mammals such regions were identified both in the 5' as well as in the 3' UTR. In all cases, RNA-binding proteins interact with these regions, yet their specific role in the observed negative regulation of translation has to be established.

In Drosophila spermatogenesis transcription occurs only premeiotically while translation can be detected also in postmeiotic spermatids. To analyse the underlying processes mst(3)gl‐9, a gene specifically expressed in the male germ cells of Drosophila melanogaster, was studied. The putative protein encoded by mst(3)gl‐9 is mostly composed of repetitive Cys‐Gly‐Pro motifs. The transcriptional and translational control of expression of mst(3)gl‐9 has been investigated by P‐mediated transformation. Only 102 bp of 5′ upstream sequences and the first 201 bp of the gene are sufficient to maintain the gene specific characteristics of expression, namely premeiotic transcription and postmeiotic translation separated by 3 days of development.