Cell cycle regulation of menin expression

The multiple endocrine neoplasia type 1 gene product, menin, interacts with Jun D. The physiological role of menin in cell cycle control and the manne r in which its inactivation contributes to tumorigenesis remain unknown. In the present study, the expression of menin was examined at various cell cy cle stages in GH4C1 cells, a rat pituitary cell line. Cells synchronized at the G(1)-S-phase boundary expressed menin at a lower level than G(0)-G(1)- synchronized cells. The expression of menin increased as the cells entered S phase, at which time Jun D expression also increased. In contrast, cells synchronized at the G(2)-M phase expressed lower levels of menin. At G(0)-G (1), G(1)-S, and G(2)-M phases of the cell cycle, menin was found predomina ntly in the nucleus. In summary, we show that in pituitary cells, menin is a nuclear protein whose expression is cell-cycle regulated. The data sugges t that menin has an important role in cell growth regulation.