Identification of a low‐M_r acidic nuclear protein as prothymosin α

Abstract

We have purified to homogeneity a lij-kDa perchloric acid (PCA)-soluble protein from rat thymus nuclei. This highly acidic protein showed a M, of ca. 30 kDa in acetic acid/urea gels, probabty due to oligomer formation. Sequence analysis of internal tryptic and the~ol~c peptides revealed that the purified protein is, in fact, prothymosin u, a very hydrophilic polypeptide, which has been previously classified as a thymic or immunomodulating hormone. We found that prothymosin G( is a rather abundant nuclear protein in rat thymus; its concentration is comparable to that of a well-characterized nonhistone protein HMG-14. The subcellular localization and physicochemical properties of prothymosin c( suggest that its function is related to those of other long polyacidic regions containing nuclear proteins.

Proteomic analysis of mouse thymoma EL4 cells treated with bis(tri-n-butyltin)oxide (TBTO)

“…A down-regulation of the ProT gene by TBTO was also observed in rat primary thymocytes (Baken, personal communication). The Western blot analysis result lends support to the observed downregulation of ProT in the TBTO-exposed cells (Figure 3) though further study is required to shed light on whether ProT selectively binds with another protein, or forms an oligomer on SDS-PAGE electrophoresis as previously reported (Palvimo and Linnala-Kankkunen, 1990;Codero et al, 1992) This small nuclear protein (M r = 12122 Da) is found in all mammalian tissues (Evstafieva et al, 2000).…”

“…A specific interaction of ProT with the basic histone H1 in vitro was previously reported (Papamarcaki and Tsolas, 1994;Karetsou et al, 1998). Alternatively, the observed band may be an oligomeric form of ProT, since previous studies showed that proT exhibits anomalous behavior on SDSelectrophoresis, forming oligomers even under denaturing and reducing conditions (Palvimo and Linnala-Kankkunen, 1990;Codero et al, 1992).…”

Regulation of prothymosin α by estrogen receptor α: molecular mechanisms and relevance in estrogen-mediated breast cell growth

“…Certain aspects of PTa structure may be useful in understanding the transcriptional regulatory function of PTa. Because of the high acidity of the protein (Palvimo and Linnala-Kankkunen, 1990) it is unlikely to be a DNA binding protein. There are structural similarities between PTa and nuclear proteins known to be involved in chromatin activity, and it has been reported that PTa interacts specifically with histone H1 (Diaz-Jullien et al, 1996;GomezMarquez and Rodriguez, 1998;Karetsou et al, 1998).…”

Do Products of the myc Proto-Oncogene Play a Role in Transcriptional Regulation of the Prothymosin α Gene?

“…Prothymosin ␣ is found in the nuclei of virtually all mammalian cells (17,39,43,58) in amounts which correlate with the proliferative activity of the tissue (24,27). The thymus, with its self-renewing pool of precursor cells (2), is usually the richest source, with large amounts of the protein found in the spleen, lungs, and kidneys (16,32).…”