Fractionation by high-performance liquid chromatography of the low-molecular-mass high-mobility-group (HMG) chromosomal proteins present in proliferating rat cells and an investigation of the HMG proteins present in virus transformed cells

Abstract

The low-molecular-mass high-mobility-group (HMG) proteins from young rat thymus nuclei were fractionated by high-performance liquid chromatography. Two proteins analogous to calf HMG14 and HMGl7 were found together with a third major component HMGI similar to that found in HeLa cells [Lund et al. (1983) FEBS Lelt. 152, 363-1671. HMGI has as amino acid composition similar to but distinct from HMG14 and HMG17. The three proteins form a family of proteins with HMG14 having an amino acid composition intermediate between HMG17 and HMGI. HMGI is present in proliferating fibroblasts and embryos but is present in very low levels in rat liver, a non-dividing tissue, supporting the notion that HMGI is required for proliferating cells. Fibroblasts transformed with avian sarcoma virus have high levels of HMGI and an additional band HMGI' but the presence of HMGI and HMGI' is not dependent on a functional src gene product.Mammalian and avian cells contain two major lowmolecular-mass HMG proteins, HMG14 and HMG17 [I], which have been implicated in modifying the chromatin structure of transcriptionally active genes [2]. Previous studies have shown that all terminally differentiated cells so far studied have these two proteins plus some minor components termed HMG18, HMG19A and HMG19B [3, 41. However recently Lund et al. [5] isolated an HMG-like protein (HMGI) from Hela cells with an electrophoretic migration on acid/ urea gels slower than calf HMG14 and HMG17 and which had an amino acid composition somewhat different from that of Hela HMG17 and that of the avian and mammalian proteins described in this laboratory [3]. It was suggested that this protein may be specific to proliferating cells. However it was not clear whether or not this protein was the human equivalent of HMG14. It was also not known whether this protein was species-specific (i.e. human) or tissue-specific.In this paper we report our results from studies with rat fibroblasts transformed with the avian sarcoma virus in which we observed, in addition to the normal HMG14 and HMG17, a doublet of proteins migrating behind HMG14 on acid/urea gels, in the position reported for human HMGI. Also rat thymus from 4 -6-week-old rats, a tissue which has a high content of proliferating cells at this age, contained an additional single protein migrating near the HMGI position. Rat liver with few dividing cells did not have these additional bands. In order to investigate the relationship between these additional HMG proteins found in proliferating rat tissues, the HMGI protein found in Hela cells, and the wellcharacterized HMG14 and HMG17 protein, we have fractionated the low-molecular-mass HMG proteins in proliferating rat thymus by HPLC and have compared the proteins with those previously isolated. We show that rat thymus nuclei have, in addition to HMG14 and HMGl7 a major additional component with amino acid composition similar to Hela HMGI. This rat HMGI is quite distinct from rat HMG14 and HMGl7 and the minor HMG18/19 proteins. EXPERIMENTAL METHODS Fractionation of HMG pr...

The expression of HMGA genes is regulated by their 3′UTR

“…An increased HMGA1 gene expression has been considered as a general diagnostic marker for neoplastic transformation (Goodwin et al, 1985;Giancotti et al, 1987Giancotti et al, , 1989 and the metastatic potential of malignant neoplasms (Bussemakers et al, 1991;Tamimi et al, 1993;Chiappetta et al, 1995).…”

Tumor promoter induces high mobility group HMG-Y protein expression in transformation-sensitive but not -resistant cells

“…HMG-I(Y) expression is also elevated in human uterine leiomyomata and pulmonary chondroid hamartomas, benign neoplasms (Williams et al, 1997;Xiao et al, 1997). HMG-I(Y) levels are high in neoplastic compared to normal cell lines (Goodwin et al, 1985;Giancotti et al, 1985Giancotti et al, , 1987. Increasing levels of HMG-I(Y) are found with progression in a series of cell lines isolated from the Dunning rat model system of prostate cancer (Bussemakers et al, 1991), as well as from a mouse mammary epithelial cell system (Ram et al, 1993), where increasing levels of both HMG-I(Y) mRNAs and proteins correlated with increasing metastatic potential of the tumors.…”

Fractionation and identification of metaphase-specific phosphorylated forms of high-mobility-group proteins

“…Goodwin et al [5] have found that HMG I is present at elevated levels in proliferating rat cells compared to nondividing rat cells, supporting the notion that HMG I is required for proliferation.…”