INTRANUCLEAR DISTRIBUTION OF HMGI Y PROTEINS - AN IMMUNOCYTOCHEMICAL STUDY/

The intranuclear distribution of HMGI/Y proteins was analyzed by immun ofluorescent staining in several cell lines using a polyclonal antibod y that stained a fibrogranular network. In actively growing 3T3 fibrob lasts, HMGI/Y proteins were mainly localized to heterochromatin masses , whereas in quiescent cells they were more diffusely distributed. Dou ble labeling experiments showed a co-localization of HMGI/Y with DNA t opoisomerase II alpha. These results are in agreement with previously published biochemical data and indicate a possible involvement of HMGI /Y proteins in several nuclear functions, including chromatin organiza tion and gene expression.