S. Haynes, C. Shunk. The interaction of hnRNP proteins with nascent transcripts represents an early control point for post-transcriptional regulation. Mutations in either of the Hrb genes are homozygous viable, but double mutants are synthetic lethals.
Death occurs during embryogenesis, and a wide variety of defects are seen.
This synthetic lethality is specific for the Hrb genes, since combinations of mutations in other hnRNP protein genes are viable. Embryonic lethality can be rescued by expression of either Drosophila protein or the human hnRNP A1 protein under the control of a heat shock promoter. This result demonstrates that the human protein can provide all the essential functions of the Drosophila proteins. In contrast to mutations in single Hrb genes, mutations in the caz gene cause pupal or pharate adult lethality, indicating that caz is essential for viability. The mutants show numerous defects, including transformation of arista to leg, missing bristles on the head and abnormal abdominal cuticle.