EXPRESSION AND SUBCELLULAR-LOCALIZATION OF MOUSE 20S PROTEASOME ACTIVATOR COMPLEX PA28

We have cloned the mouse PA28 proteasome activator cDNAs, Northern blo t demonstrates high PA28 mRNA levels in liver, kidney and lung, mRNA l evels are low in thymus, spleen and brain, In contrast, PA28 protein l evels vary little between these tissues, Immunocytological analysis an d cell fractionation experiments demonstrate. that both subunits are a lmost equally distributed between the cytoplasm and the nucleus, Inter estingly, PA28 alpha spares nucleoli, while PA28 beta is strongly enha nced in. the nucleolus, This indicates for the first time that the PA2 8 alpha and PA28 beta subunits may serve nuclear functions which may b e different from and independent of each other, (C) 1997 Federation of European Biochemical Societies.