The centrosomal localization of KM-HN-1 (MGC33607) depends on the leucine zipper motif and the C-terminal coiled-coil domain

KM-HN-1 is a C-terminal coiled-coil domain containing protein previously referred to as image clone MGC33607. This protein has been previously identified as a cancer/testis antigen and reported as nuclear and chromatin localizing protein. We raised polyclonal antisera with the GST fusion protein and identified them as a 105 kDa protein. Motif analysis showed that this protein harbors the leucine zipper motif in internal 1/3 region and the coiled-coil domain in the C-terminal region. Using the full length and various deletion mutants, we determined the motif that governs the subcellular localization of KM-HN-1. Immunofluorescence staining of the endogenous KM-HN-1 and various kinds of GFP-tagged KM-HN-1 revealed that KM-HN-1 localizes to the centrosomes as well as nucleus. The centrosomal localization-determining region of this protein is C-terminal coiled-coil domain in which the leucine zipper motif and the nuclear export signal (NES) harbor.

Thioacetamide effects on the polypeptidic and nucleoporin pattern and chemical composition of rat liver nuclear envelope subfractions

The effect of the administration of seven doses of the hepatocarcinogen thioacetamide on the chemical composition of rat liver nuclear envelope subfractions: associated chromatin, nuclear membranes and pore complex-lamina fraction, is analyzed. No alteration in DNA, RNA or phospholipid content is observed after the hepatocarcinogen treatment. Electrophoretic studies of each subfraction from thioacetamide treated rats show differences in the relative proportions of some polypeptides when compared with the controls. Examination of the wheat germ agglutinin binding polypeptides of each subfraction reveals a decrease in the stain of two pore complex-lamina nucleoporins of 85 and 164 kDa and an increase in one of 93 kDa; this observation can be due to changes in the quantity and/or in the agglutinin binding capacity of the nucleoporin as a result of thioacetamide administration. In view of the participation of nucleoporins in the nucleocytoplasmic transport, the changes observed suggest a relationship between changes of some O-linked N-acetyl glucosamine polypeptides components of the nuclear pore complex and the altered transport of some RNA species observed after thioacetamide administration.

Hepatocellular carcinoma cell type specific interaction of P105 and P98 nuclear factors with laminin B1 and B2 genes.

Laminin is a major glycoprotein specific to basement membranes. Hepatocellular carcinoma tissue synthesize and secrete abundant laminin. By DNA-protein interaction assays, we have identified nuclear factors specific to hepatocellular carcinoma cells. The comparison of nuclear factor binding by Southwestern analysis with B1 and B2 laminin promoters revealed different patterns of nuclear factor binding in different cells types. In hepatocellular carcinoma, HepG2 cells, a specific pair of proteins (P105 and P98) consisting of 105 and 98 kDa were identified as common nuclear factors for both B1 and B2 laminin promoters, while in completely diverse human glioma cells (U251), various different and greater number of nuclear proteins ranging from 212 to 68 kDa were detected to interact separately with laminin B1 and B2 genes.