H1-DEGREES AND H3.3B MESSENGER-RNA LEVELS IN DEVELOPING RAT-BRAIN

Two overlapping rat cDNAs, covering a continuous region of 1107 base p airs, have been isolated and sequenced. The clones contain identical o pen reading frames, encoding a 136 amino acid long polypeptide which e xhibits 100% identity to other mammalian H3.3 histone variants. We sho w that the inserts derive, in particular, from the H3.3B gene. We used these inserts and an insert from an H1 degrees encoding clone, previo usly described (6), as probes to study the accumulation of mRNAs encod ing the corresponding histone replacement variants (namely; H1 degrees and H3.3) during rat brain development. We found that the concentrati on of both H1 degrees and H3.3B mRNAs decreases from the embryonal day 18 (E18) to the postnatal day 10 (P10), with inverse correlation to p rotein accumulation.