The histones of Caenorhabditis elegans: no evidence of stage-specific isoforms. An overview.

The nematode Caenorhabditis elegans expresses one species of H2A and one species of H4 molecules, at least two species of H1 (H1.1, H1.2), two species of H2B (H2B.1, H2B.2) and 2-4 species of H3 (H3.1 and H3.3 and an unassigned Ile/Leu microheterogeneity in H3). The study of their primary structures has been completed now and all of them, with the exception of the Ile/Leu microheterogeneity in H3, have been assigned to protein spots on two-dimensional gels. One spot, previously designated H3.2, probably represents C-terminally cleaved H3.1. The relative abundance of the isohistones was essentially the same when derived from either eggs, gravid adults or postreproductive, senescent worms. The degree of post-translational modification, however, particularly acetylation of H2A, H2B and H3 histone species, was reduced at old age.