DROSOPHILA-MELANOGASTER HISTONE H2B RETROPSEUDOGENE IS INSERTED INTO A REGION RICH IN TRANSPOSABLE ELEMENTS

We have isolated and characterized the genomic sequence of a Drosophil a melanogaster histone H2B pseudogene that is localized outside of the cluster of the replication-dependent histone genes and has all the pr operties of a retropseudogene. It is highly homologous to the transcri bed region of the D. melanogaster histone H2B gene, but not to its fla nking regions, and is surrounded by short direct repeats. The pseudoge ne contains several point mutations that preclude its translation. The sequence of the 3' region of this pseudogene is compatible with the h ypothesis that the 3' terminal stem-loop structure of the histone H2B mRNA has served as a primer for the reverse transcription event from w hich this pseudogene originated. Analysis of the regions flanking the histone H2B pseudogene revealed the presence of three different types of transposable elements, suggesting that this chromosomal locus repre sents a hotspot for transposition.