Low levels of NPM gene expression in UV-sensitive human cell lines

Nucleophosmin (NPM) is a major nuclear matrix protein associated with neopl astic: growth in various cell types. We recently suggested that expression of the NPM gene is involved in an increased resistance to UV irradiation in human cells against the cell-killing effects of UV (mainly 254nm wavelengt h far-ultraviolet ray) [Y. Higuchi, K. Kita, H. Nakanishi, X-L. Wang, S. Su gaya, H. Tanzawa, H. Yamamori, K. Sugita, A. Yamaura, N. Suzuki, Biochem. B iophys. Res. Commun. 248 (1998) 597-602]. In the present study, expression levels of the NPM gene were examined in human cell lines with a high sensit ivity to UV cell-killing. Cockayne syndrome patient-derived cell lines, CSA I and CSBI, and the Xeroderma pigmentosum patient-derived cell line, XP20S( SV), XP13KY, XP3KA, XP6BE(SV), XP101OS and XP3BR(SV), have been investigate d for their NPM mRNA expression with Northern blotting analysis. All of the se UV-sensitive cells demonstrated lower expression levels compared with th ose of normal fibroblast cells. FF, or an UV-resistant cell line, UHr-10; q uite a lower level of expression in XP205(SV) cells after UV irradiation in contrast to a distinguishable increase in the expression in UVr- cells. Th ese results confirmed an intimate correlation between degree of UV sensitiv ity and expression levels of the NPM gene in human cells. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.