Cloning and expression of a novel nuclear matrix-associated protein that is regulated during the retinoic acid-induced neuronal differentiation

Retinoic acid (RA), a derivative of vitamin A, is essential for the normal patterning and neurogenesis during development. RA treatment induces growth arrest and terminal differentiation of a human embryonal carcinoma cell li ne (NT2) into postmitotic central nervous system neurons. Using RNA fingerp rinting by arbitrarily primed polymerase chain reaction, we identified a no vel serine/threonine-rich protein, RA-regulated nuclear matrix-associated p rotein (Ramp), that was down-regulated during the RA-induced differentiatio n of NT2 cells. Prominent mRNA expression of ramp could be detected in adul t placenta and testis as well as in ah human fetal tissues examined. The ge nomic clone of ramp has been mapped to the telomere of chromosome arm 1q, c orresponding to band 1q32.1-32.2. Associated with the nuclear matrix of NT2 cells, Ramp translocates from the interphase nucleus to the metaphase cyto plasm during mitosis, During the late stage of cytokinesis, Ramp concentrat es at the midzone of the dividing daughter cells. The transcript expression of ramp is closely correlated with the cell proliferation rate of NT2 cell s. Moreover, overexpression of Ramp induces a transient increase in the pro liferation rate of NT2 cells. Taken together, our data suggest that Ramp pl ays a role in the proliferation of the human embryonal carcinoma cells.