Testis-specific histone H1t is antigenically distinct among H1 subtypes.

Histone H1t has been purified from rat testes and antibodies were elicited in rabbits. Immunoblotting studies with anti-histone H1t-IgG have shown that it reacted specifically with histone H1t but not with other histone H1 subtypes, namely H1a, -b, -c, -d, -e and H10. The anti-histone H1t-IgG also did not react with chicken erythrocyte histone H5. Immunoblotting studies have also revealed that the polyclonal anti-histone H1t-IgG reacted with (a) two polypeptide fragments, NBS-N and NBS-C, derived from N-bromosuccinimide cleavage of histone H1t, (b) two polypeptide fragments, CT-N and CT-C, derived from alpha-chymotrypsin cleavage of histone H1t, and (c) GH1t, globular domain of histone H1t obtained after trypsin cleavage. The indirect immunofluorescence studies on nuclei isolated from adult rat testes with anti-histone H1t-IgG showed that the fluorescence, particularly, of the pachytene nucleus was the brightest. On the other hand, anti-histone H1t-IgG did not stain nuclei from either liver or nuclei isolated from the testes of 10-day-old rats.