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The Drosophila Hrb87F gene encodes a new member of the A and B hnRNP protein group.

ABSTRACT: Nascent premessenger RNA transcripts are packaged into heterogeneous nuclear ribonucleoprotein (hnRNP) complexes containing specific nuclear proteins, the hnRNP proteins. The A and B group proteins constitute a major class of small basic proteins found in mammalian hnRNP complexes. We have previously characterized the Drosophila melanogaster Hrb98DE gene, which is alternatively spliced to encode four protein isoforms closely related to the A and B proteins. We report here that the Drosophila genome contains a family of genes related to the Hrb98DE gene. One member of the family, Hrb87F, is very homologous to Hrb98DE in both sequence and structure. The Hrb87F transcripts (1.7 and 2.2 kb) utilize two alternative polyadenylation sites, are abundant in ovaries and early embryos, and are present in lesser amounts throughout development. In one wildtype strain of Drosophila there is a naturally-occurring polymorphism in this gene due to the insertion of a 412 transposable element in the 3' untranslated region. The larger transcript is not produced in these files and thus is not required for viability. Sequence identities among the Drosophila Hrb proteins and the vertebrate A and B hnRNP proteins suggest that these proteins may form a distinct subfamily within the larger family of related RNA binding proteins.

SUBMITTER: Haynes SR

PROVIDER: S-EPMC333530 | biostudies-other | 1991 Jan

REPOSITORIES: biostudies-other

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The Drosophila Hrb87F gene encodes a new member of the A and B hnRNP protein group.

Haynes S R SR Johnson D D Raychaudhuri G G Beyer A L AL

Nucleic acids research 19910101 1

Nascent premessenger RNA transcripts are packaged into heterogeneous nuclear ribonucleoprotein (hnRNP) complexes containing specific nuclear proteins, the hnRNP proteins. The A and B group proteins constitute a major class of small basic proteins found in mammalian hnRNP complexes. We have previously characterized the Drosophila melanogaster Hrb98DE gene, which is alternatively spliced to encode four protein isoforms closely related to the A and B proteins. We report here that the Drosophila gen ...[more]

PMID: 1849257

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Project description:BackgroundThe uropathogenic specific protein (Usp) and three OrfU proteins (OrfU1, OrfU2 and OrfU3) are encoded in the putative small pathogenicity island which is closely associated with Uropathogenic Escherichia coli. Although homology search revealed that Usp and OrfUs have a homology with nuclease-type bacteriocins, which possess H-N-H nuclease motif, and immunity proteins respectively, the molecular activity of these proteins was never investigated. In this study, we try to over-express Usp in E. coli, purify Usp and characterize its molecular activity.MethodRecombinant Usp protein was expressed in E. coli BL21(DE3) cells together with 6× Histidine tagged OrfU1 (OrfU1-His) protein, and purified with affinity chromatography using Ni2+ chelating agarose. The nuclease activity of the purified Usp was examined in vitro by using plasmid DNA as a substrate. The importance of H-N-H motif in nuclease activity of Usp was examined by site-directed mutagenesis study.ResultsWe revealed that pET expression vector encoding Usp alone could not be maintained in E. coli BL21(DE3), and insertion of the orfUs as well as usp in the constructed plasmid diminished the toxic effect, suggesting that co-expressed OrfUs masked the activity of Usp. To purify Usp protein, we employed the expression vector encoding untagged Usp together with OrfU1-His. A tight complex formation could be observed between Usp and OrfU1-His, which allowed the purification of Usp in a single chromatographic step: binding of Usp/OrfU1-His complex to Ni2+ chelating agarose followed by elution of Usp from the complex with denaturing reagent. The purified free Usp was found to have the nuclease activity, and the activity was constitutively higher than Usp/OrfU1-His complex. H-N-H motif, which is found in various types of nucleases including a subfamily of nuclease-type bacteriocin, had been identified in the C-terminal region of Usp. Site-directed mutagenesis study showed that the H-N-H motif in Usp is indispensable for its nuclease activity.ConclusionThis is the first evidence of the molecular activity of the new member of H-N-H superfamily and lays the foundation for the biological characterization of Usp and its inhibitor protein, OrfUs.

Project description:The family of mammalian O-mannosyltransferases includes two enzymes, POMT1 and POMT2, which are thought to be essential for muscle and neural development. Similar to mammalian organisms, Drosophila has two O-mannosyltransferase genes, rotated abdomen (rt) and DmPOMT2, encoding proteins with high homology to their mammalian counterparts. The previously reported mutant phenotype of the rt gene includes a clockwise rotation of the abdomen and defects in embryonic muscle development. No mutants have been described so far for the DmPOMT2 locus. In this study, we determined that the mutation in the twisted (tw) locus, tw(1), corresponds to a DmPOMT2 mutant. The twisted alleles represent a complementation group of recessive mutations that, similar to the rt mutants, exhibit a clockwise abdomen rotation phenotype. Several tw alleles were isolated in the past; however, none of them was molecularly characterized. We used an expression rescue approach to confirm that tw locus represents DmPOMT2 gene. We found that the tw1 allele represents an amino acid substitution within the conserved PMT domain of DmPOMT2 (TW) protein. Immunostaining experiments revealed that the protein products of both rt and tw genes colocalize within Drosophila cells where they reside in the ER subcellular compartment. In situ hybridization analysis showed that both genes have essentially overlapping patterns of expression throughout most of embryogenesis (stages 8-17), while only the rt transcript is present at early embryonic stages (5 and 6), suggesting its maternal origin. Finally, we analyzed the genetic interactions between rt and tw using several mutant alleles, RNAi, and ectopic expression approaches. Our data suggest that the two Drosophila O-mannosyltransferase genes, rt and tw, have nonredundant functions within the same developmental cascade and that their activities are required simultaneously for possibly the same biochemical process. Our results establish the possibility of using Drosophila as a model system for studying molecular and genetic mechanisms of protein O-mannosylation during development.

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The Drosophila Hrb87F gene encodes a new member of the A and B hnRNP protein group.

Publications

The Drosophila Hrb87F gene encodes a new member of the A and B hnRNP protein group.

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