High impact information on Hrb87F

• Indirect immunofluorescence shows that, after prolonged heat-shock, the P11 antigen is present only in the heat-shock puff 93 D. Identical distribution patterns were obtained with another monoclonal antibody, Q18 [1].
• Unlike P11, this antibody also cross-reacts with D. hydei and D. virilis polytene chromosomes, where the puffs 48 B and 20 CD, respectively, are the only loci prominently stained after heat-shock [1].
• The resulting deletion, B52(28), is confined to the B52 gene and its neighbor the Hrb87F gene [2].
• Here we use band shift experiments to show that RNA binding patterns are altered when Sxl is combined with other proteins having similar glycine-rich domains, including mammalian heterogeneous nuclear (hn) RNP L and Drosophila Hrb87F (an hnRNP A/B homolog) [3].
• Altered levels of the Drosophila HRB87F/hrp36 hnRNP protein have limited effects on alternative splicing in vivo [4].

Biological context of Hrb87F

• 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 [5].
• Like NonA, X4/PEP, S5, and P11/Hrb87F are present on active sites on polytene chromosomes [6].
• Three other proteins present in the complex have been identified: X4/PEP (protein on ecdysone puffs), a 100-kDa zinc finger RNA-binding protein; the 70-kDa S5 protein, an as yet uncharacterized RNA-binding protein; and P11/Hrb87F, a 38-kDa RRM protein homologous to hnRNP protein A1 from mammals [6].
• The character of odor-induced responses was more profound and complex later in development; small, tonic increases in firing frequency were observed at pupal stages P8 through P11 (ii), while in older pupae and young adults approximately 25% of the increased responses were phasic-tonic [7].

Other interactions of Hrb87F

• One member of the family, Hrb87F, is very homologous to Hrb98DE in both sequence and structure [5].
• Using overexpression and deletion mutants of Hrb87F, we have tested the hypothesis that the ratio of A/B hnRNP proteins to SR family proteins modulates certain types of alternative splice-site selection [4].
• The P11 sequence corresponds to the Hrb87F sequence that was recently described by Haynes et al [8].

Analytical, diagnostic and therapeutic context of Hrb87F

• The small and giant RNP complexes previously described in these puffs were also observed in puff 93 D. Both types of particle contain the P11 antigen as shown by immunoelectron microscopy [1].
• Here we show by density centrifugation and enzyme-linked immunosorbent assay tests that the P11 antigen is part of nuclear ribonucleoprotein (RNP) complexes [1].
• Immunofluorescence analysis of polytene chromosomes of Drosophila melanogaster using the monoclonal antibody P11 has shown that after heat-shock the 38-kDa P11 antigen almost exclusively localizes at heat-shock puff 93D where it is part of giant puff-specific RNP granules [9].

References