Structure and Function of A Novel Nuclear Matrix Protein : N/MAX

点击翻译按钮获取中文摘要

cDNA clones encoding a DNA binding protein (hN/MAX) of more than 1870 amino acide were isolated from cDNA libraries of various human cells. N/MAX is a novel nuclear matrix protein which preferentially binds to cytidine clusters in either strand of double stranded DNA.The domain essential for DNA binding was located near C-terminal of N/MAX.Indirect immunofluorescence microscopy with an antibody against N/MAX showed stain of internal fibrogranular structure but not necleolus of HeLa cell nucleus. This stain was excluded from condensed chromatin appeared during M-phase. Western blot analysis showed a 250 kDa protein enriched in nuclear matrix fraction. N/MAX shares three types of domains (MH1, MH2 and MH3) with rat matrin 3. MH1 is a 43 amino acid sequence at N-terminal of both nuclear matrix proteins. MH2 is ca, 70 amino acid sequence repeated twice and three times in matrin 3 and N/MAX,respectively. This domain has high homology to RNA binding motif found in hnRNP I/L.MH3 is a 60 amino acid sequence located at the C-terminus of both proteins. M/MAX has an arginine and serine rich (RS) domain at N-terminal side of MH1 repeats. Close to the domain essential for DNA binding, there are nine times repeated suquences with consensus of LVTVDEVIEEEDL.This domain can bind to calcium and the DNA binding abillity of N/MAX was affected by calcium at concentration range less than 0.1 mM.cDNA clones of mouse equivalent (mN/MAX) showed high homology to hN/MAX and a 75 amino acid sequence extending to N-terminal side of RS domain was perfectly conserved. This domain had a zinc fingerlike sequence. Mouse cDNA clones suggested the pressence of more than two types of N/MAX mRNAs probably produced by alternative splicing of the N/MAX gene.