A 210 kDa protein named GANP is upregulated in germinal center (GC)-B cells in the spleen of antigen-immunized mouse. We studied a human ganp gene (hganp) encoding a putative polypeptide of 1980 amino acids. The carboxyl-terminal 721-amino-acid sequence of hGANP is identical to Map80, that is presumably generated by alternative splicing of hganp/Map80 gene. The genomic segment carrying hganp and Map80 genes was isolated, and the chromosomal location was determined on 21q22.3. Northern blot analysis with RNAs from various organs demonstrated a single band of 7 kb hganp mRNA, which suggests a preferential transcription of hganp gene from the hganp/Map80 locus. The hGANP expression was upregulated in GCs of the tonsil, as demonstrated by in-situ RNA hybridization and immunohistochemical analyses. The hGANP, with the domain (Map-box) capable of binding to MCM3 in B cells, might be involved in regulation of cell-cycle progression and DNA replication of GC-B cells. (C) 2000 Elsevier Science B.V. All rights reserved.
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