ISOLATION AND CHARACTERIZATION OF A CDNA FROM A HUMAN HISTONE H2B GENE WHICH IS RECIPROCALLY EXPRESSED IN RELATION TO REPLICATION-DEPENDENT H2B HISTONE GENES DURING HL60 CELL-DIFFERENTIATION

A variant human histone H2B cDNA (HHC289) has been cloned and characterized and shown to have a complex pattern of regulation with respect to the HeLa S3 cell cycle and HL60 cell differentiation. The H2B protein coding region of HHC289 is flanked at the 3' end by a 1798-nt nontranslated trailer that contains a region of hyphenated dyad symmetry and a poly(A) addition sequence, followed by a poly(A) tail. Nuclear run-on transcription analysis revealed a 2-fold increase in transcription of the HHC289 gene during S phase, in comparison to replication-dependent human histone genes which exhibit a 2-3-fold increase in transcription during S phase. Northern blot analysis indicated that the levels of the 2300-nt HHC289 mRNA species did not vary significantly during the HeLa S3 cell cycle, in comparison to replication-dependent H2B mRNAs which are elevated 15-fold during S phase. Northern blot analysis also revealed a reciprocal relationship during the onset of HL60 differentiation between the expression of the HHC289 H2B gene and the replication-dependent H2B genes. The levels of the 2300-nt HHC289 H2B species increased approximately 10-fold during HL60 cell differentiation whereas the levels of cell cycle dependent H2B mRNAs decreased to less than 1% of those in proliferating cells. These results suggest that complex transcriptional and posttranscriptional regulatory mechanisms control cellular levels of mRNAs from various human H2B histone genes during progression through the cell cycle and at the onset of differentiation.