GENETIC AND MOLECULAR ANALYSIS OF THE X-CHROMOSOMAL REGION 14B17-14C4IN DROSOPHILA-MELANOGASTER - LOSS OF FUNCTION IN NONA, A NUCLEAR-PROTEIN COMMON TO MANY CELL-TYPES, RESULTS IN SPECIFIC PHYSIOLOGICAL AND BEHAVIORAL DEFECTS

We have performed a genetic analysis of the 14C region of the X chromo some of Drosophila melanogaster to isolate loss of function alleles of no-on-transient A (nonA; 14C 1-2; 1-52.3). NONA is a nuclear protein common to many cell types, which is present in many puffs on polytene chromosomes. Sequence data suggest that the protein contains a pair of RNA binding motifs (RRM) found in many single-strand nucleic acid bin ding proteins. Hypomorphic alleles of this gene, which lead to aberran t visual and courtship song behavior, still contain normally distribut ed nonA RNA and NONA protein in embryos, and in all available alleles NONA protein is present in puffs of third instar larval polytene chrom osomes. We find that complete loss of this general nuclear protein is semilethal in hemizygous males and homozygous cell lethal in the femal e germline. Surviving males show more extreme defects in nervous syste m function than have been described for the hypomorphic alleles. Five other essential genes that reside within this region have been partial ly characterized.