Drosophila snRNP associated protein P11 which specifically binds to heat shock puff 93D reveals strong homology with hnRNP core protein A1.

We have isolated cDNAs coding for a ribonucleoprotein of Drosophila melanogaster that is distinguished by its nearly exclusive presence at only one of the several heat shock puffs in polytene chromosomes of third instar larvae. We determined the nucleotide sequence and deduced the corresponding amino acid sequence. Its coding capacity for a 39 kDa protein is consistent with the size of the protein detected by the monoclonal antibody P11 used for expression cloning. Our results show that the P11 protein belongs to the category of hnRNP proteins of bipartite structure: the amino-terminal half contains two RNA binding domains and the carboxyterminal half is rich in glycine residues. Analysis of the genomic structure revealed two introns located within the coding portion of the gene and a third one in the 3'untranslated region. We detect two different polyadenylation sites as a result of alternative termination-polyadenylation. Its strong sequence homology with hnRNP A1 protein and its previously shown association with snRNP particles indicates that a typical hnRNP protein may also exist in a complex with snRNP particles. The P11 sequence corresponds to the Hrb87F sequence that was recently described by Haynes et al. (1) as hnRNP A related gene.