Binding of doa kinase to specific loci in polytene chromosomes of Drosophila melanogaster.

OBJECTIVES

Highly conserved LAMMER kinases belong to the family of dual-specific proteins phosphorylating enzymes with homologues in yeast, plants, Drosophila and mammals. SR proteins, several members of which are components of the spliceosomal complex and have been implicated in the control of alternative splicing, were identified among first targets of LAMMER kinases. The Drosophila locus Darkener of apricot (Doa) encodes best known representative of the LAMMER family of kinases, which is essential for embryonic and postembryonic development, neurogenesis, differentiation of photoreceptors, and sex determination.

METHODS

DOA kinase was detected on squash preparations of polythene chromosomes using anti-DOA antibodies in combination with indirect immunofluorescence.

RESULTS

Here we provide evidence for active chromosomal presence of DOA kinase in Drosophila salivary glands, and increased abundance of DOA at eleven specific loci of polythene chromosomes where it can be involved in on-site control of splicing process. Many genes that may be found at the loci with increased abundance fall into three major groups based on their known functions. First group contains genes that code for transcription factors, RNA-binding proteins or chromatin modifying enzymes. Second group of genes encode proteins which belong to proteasomal components, lipid enzymes, stress-sensitive ER proteins and caspases which are all early/proximal components of apoptotic process. Third group of genes comprises of tRNA coding genes or genes of tRNA synthases (ligases), all involved in protein synthesis. Some of the encoded protein products are confirmed or potential substrates of DOA kinase activity.

CONCLUSIONS

Data indicate that genes encoding proteins involved in closely related pathways are concentrated at certain loci to achieve more efficient regulation of their expression as exemplified from distribution of DOA protein on Drosophila polythene chromosomes.