INS and Glucose intolerance: Fig. S5). These observations suggest that the increase in nuclei positive for p21Cip1 and p27Kip1 is due to an altered balance in the subcellular localization of these proteins. From these data, we conclude that Sei1 plays a relevant role in the maintenance and function of pancreatic β-cells. Absence of Sei1 results in higher levels of the cell cycle inhibitors p21Cip1 and p27Kip1, reduced β-cell area, decreased insulin secretion and, consequently, glucose intolerance.