HMGB4, a novel member of the HMGB family, is preferentially expressed in the mouse testis and localizes to the basal pole of elongating spermatids.
We identified HMGB4, a novel member of the HMGB family lacking the acidic tail typically found in this family. HMGB4 is strongly and preferentially expressed in the adult mouse testis and weakly in the brain, but not in many other tissues. HMGB4 associates with chromatin, and in transfection assays, in contrast to HMGB1, it acts as a potent transcriptional repressor. During spermatogenesis, HMGB4 is present in the euchromatin of late pachytene spermatocytes and haploid round spermatids, whereas stronger expression is observed during the elongation phase, where it localizes to the basal pole of the nucleus in a manner mutually exclusive with H1FNT (H1T2) localized at the apical pole. HMGB4 basal localization is lost in H1FNT-mutant spermatids, showing that H1FNT provides a positional cue for organizing chromatin domains within the nucleus. These results show that HMGB4 and H1FNT specify distinct chromatin domains at the apical and basal poles of the elongating spermatid nucleus.
Catena
Raffaella
R
ALMA Consulting Group, European Research Project Management, 69338 Lyon, France.
Escoffier
Emmanuelle
E
Caron
Cécile
C
Khochbin
Saadi
S
Martianov
Igor
I
Davidson
Irwin
I
D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D018507:Gene Expression Regulation, Developmental; D024002:HMGB Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013087:Spermatids / Q000378:metabolism*; D013737:Testis / Q000378:metabolism*; D014018:Tissue Distribution
D024002:HMGB Proteins; C539347:HMGB4 protein, mouse