Recent and rapid amplification of the sperm basic nuclear protein genes inwinter flounder

The high molecular weight basic nuclear proteins (HMrBNPs), which are tight ly bound to sperm chromatin in winter flounder, are made up of imperfect re iterations of simple peptide sequences that contain phosphorylatable DNA-bi nding motifs. Genomic Southern blots hybridized with probes to the coding a nd non-coding regions of HMrBNP mRNA showed that HMrBNP sequences form a co mplex multi-gene family. Previously, one gene (2B) was used to establish an evolutionary link between histone H1 and the HMrBNPs. Further examination of this complex, multi-gene family has now revealed that the majority of th e HMrBNP genes are linked as 4.5 kb direct tandem repeats that each contain a 2.8 kb coding region and a 1.7 kb intergenic region (IR). These findings , combined with the cloning of the IR, established that the tandemly repeat ed genes lack introns and code for the abundant 3 kb HMrBNP mRNAs that prod uce the prominent 110 kDa HMrBNP. Southern blotting of DNAs from other righ teye flounder species showed that HMrBNP multi-gene families were present i n closely related species, though with substantial differences in restricti on patterns and band intensities, but were not detected in more distantly r elated flounders. These observations are consistent with recent and rapid e laboration of the HMrBNP gene family. (C) 1999 Elsevier Science B.V. All ri ghts reserved.