Modulation of the cellular ratio of chromosomal high mobility group proteins 14 to 17 in transfected cells.

Abstract

The cDNAs coding for human nonhistone chromosomal high mobility group (HMG) proteins 14 and 17 have been introduced into the eukaryotic expression vector pSVL under the transcriptional control of the SV40 late promoter and the constructs used to transfect COS cells. Transfection with plasmid pSVL14s, containing the HMG-14 cDNA in the sense orientation, increased the endogenous levels of HMG-14 mRNA 50-fold and the levels of HMG-14 protein 3-fold. Transfection with pSVL17s, which contains the HMG-17 mRNA in the sense orientation, resulted in a 19-fold increase in mRNA levels and a 3-fold increase in the protein level. Transfection with pSVL17as, containing the HMG-17 in the antisense orientation, resulted in a noticeable decrease in the protein levels. The overproduction of HMG mRNAs does not affect the level of other cellular mRNAs and the increase in the cellular level of either HMG-14 or -17 did not affect the level of the other HMG or that of any other cellular protein examined. The results suggest that COS cells can tolerate large excess of HMG mRNAs and protein, that the relative amounts of HMG-14 and HMG-17 and their mRNAs are not constant, and that neither the transcription nor the translation of the proteins is coordinately regulated.