SEQUENCE AND TRANSCRIPT ANALYSIS OF MACRONUCLEAR HISTONE H2B GENES FROM EUPLOTES-CRASSUS

Two 1.5-kb macronuclear chromosomes bearing histone H2B genes from the ciliated protozoan Euplotes crassus were cloned and sequenced. Althou gh the noncoding sequences on these macronuclear chromosomes are very different, the genes encode an identical 113-aa histone H2B protein th at has a shortened N-terminus and a highly conserved C-terminus relati ve to histone H2B proteins in other organisms. Primer extension was us ed to determine the transcription start points. Northern analysis show s that the abundance of H2B mRNA changes relative to DNA replication p eriods during the sexual phase of the life cycle. Analysis of 3' RACE products indicates that the H2B genes are coexpressed. (C) 1997 Elsevi er Science B.V.