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.