NOVEL CRE-BINDING PROTEINS OF 11-16 KDA BIND TO THE LDH A-GENE CRE INA SEQUENCE-SPECIFIC AND HEPATOCYTE GROWTH-DEPENDENT MANNER IN PARTIALLY HEPATECTOMIZED RAT-LIVER

We examined cAMP response element (CRE)-binding proteins involved in l actate dehydrogenase A (LDH A)-gene transcription in rat liver after p artial hepatectomy. Gel retardation and Southwestern blot assays showe d that the CRE-binding activity of the 18-16 kDa novel proteins increa sed in accordance with increases in LDH A-mRNA in regenerating liver t issues, whereas that of the 43 kDa CREB did not. Using CRE-oligonucleo tide affinity chromatography and reverse-phase HPLC, we purified four CRE-binding proteins of 11.2, 15.2, 15.8, and 16.3 kDa, N-tenninal ami no acid sequences of 15.2 and 16.3 kDa proteins revealed a high sequen ce homology to but were not identical with those of rat histone H2A.1 and H2B, respectively. CRE-bindings of these two proteins were highly specific, while those of histones H2A.1 and H2B were nonspecific as sh own by competition-Southwestern blot and DNase I footprinting assays. Taking these data together , we suggest that the novel 11-16 kDa CRE-b inding proteins are responsible for the cen growth-dependent inducibil ity of LDH A-gene transcription during liver regeneration. (C) 1998 Ac ademic Press.