Pancreas acinar cell regeneration and histone (H1 and H10) modifications after partial pancreatectomy or after a protein-free ethionine regimen
Varricchio, F.; Mabogunje, O.; Kim, D.; Fortner, J.G.; Fitzgerald, P.J.
Cancer Research 37(11): 3964-3969
1977
ISSN/ISBN: 0008-5472 PMID: 332342 Document Number: 116406
Histone fractions of rat pancreas nuclei were separated by polyacrylamide gel electrophoresis during pancreas acinar cell regeneration following partial pancreatectomy (PPX) or after a protein-free ethionine (PFE) regimen. In the PPX model, earlier studies showed an increase of DNA synthesis 36 and 48 h after operation and a small increase of weight in the residual pancreas segment 2-12 mo. later. In the present study, 12-24 h after PPX, there appeared a new phosphorylated histone band of the H1 fraction that was not present 48 h postoperatively. The PFE regimen produces necrosis of most acinar cells of the pancreas, a prolonged increase of DNA synthesis and complete restitution of the pancreas, as reported earlier. In the present study, new phosphorylated H1 fractions were noted during acinar cell degeneration, and they disappeared before the increase of DNA synthesis. The appearance of phosphorylated H1 fractions before the increase of DNA synthesis in the PPX and PFE models is consistent with the suggestion that H1 phosphorylation is involved in the initiation of DNA synthesis. The lack of extensive replication in the PPX model indicates that phosphorylation of H1 histones, per se, is not adequate to maintain DNA synthesis for more than a day or 2. A decrease of a minor histone, the H1o band, before and during the increase of DNA synthesis, occurs in the PFE regimen. H1o was a doublet; both bands showed parallel decreases before and throughout the period of increased DNA synthesis, and they returned to normal after DNA synthesis reached control levels. The decrease of the H1o doublet may be causally related to the increase of DNA synthesis, or it may indicate changes in the DNA-histone complex associated with replication.