HUMAN MYELOID CELL NUCLEAR DIFFERENTIATION ANTIGEN BINDS SPECIFICALLYTO NUCLEOLIN

The human myeloid cell nuclear differentiation antigen (MNDA) is a nuc lear protein expressed specifically in cells of the myelomonocytic lin eage and regulated by interferon alpha in a cell-specific fashion. MND A is also a member of a family of interferon-regulated genes of unknow n function. In an effort to elucidate the function of MNDA, three tech niques (affinity purification, coimmunoprecipitation, and protein blot assay) were used to characterize its specific protein binding activit ies. Microsequence analysis showed that MNDA bound the 100 kDa nucleol in protein. The identification of nucleolin was confirmed by immunorea ction with specific antibodies. MNDA contains motifs which could accou nt for specific binding to nucleolin. Nucleolin binds other macromolec ules and exhibits features consistent with roles in signal transductio n, production of ribosomes, nuclear matrix structure, and regulation o f transcription. The present results indicate that the function of MND A is most likely related to interactions with other proteins. Through these associations, MNDA could contribute cell/lineage- and differenti ation-specifc limits to the function of ubiquitous proteins such as nu cleolin. Further analysis of MNDA protein binding could be critical to elucidating the function of MNDA and could contribute to understandin g the function of the products of other members of this interferon-ind ucible family of genes. (C) 1995 Wiley-Liss, Inc.