伊藤 美紀子

The cDNA clone encoding HMG 2a of chick liver was isolated from a lambda-gt11 expression library using polyclonal antibodies. DNA sequence analysis revealed an open reading frame of 201 amino acids. Comparison of the nucleotide sequences of cDNA coding for chick liver HMG 2a with pig thymus HMG 2 and human monocytic leukemia cell HMG 2 showed 70% homology. 2.0 kb and 1.2 kb mRNAs were found in newly hatched chick liver and decreased during postnatal development of chicks.

Monoclonal antibodies were prepared against the high mobility group (HMG) protein 2b from chick liver chromatin and a monoclonal-antibody-based enzyme-linked immunosorbent assay (ELISA) was developed for chick HMG 2b. The sensitivity of the assay is about ten times that of the previously described radioimmunoassay and solid-phase enzyme immunoassay for HMG proteins. With the use of ELISA technique, the amount of HMG 2b (mu-g protein/mg DNA) in the livers of 1-day old and 70-day old chicks was found to be 2.56 +/- 0.4, and 1.20 +/- 0.2, respectively. The age-dependent change in the level of HMG proteins probably reflects changes in the functional state of chromatin during ageing.