Human sperm telomere-binding complex involves histone H2B and secures telomere membrane attachment

Telomeres are unique chromatin domains located at the ends of eukaryotic ch romosomes. Telomere functions in somatic cells involve complexes between te lomere proteins and TTAGGG DNA repeats. During the differentiation of germ- line cells, telomeres undergo significant reorganization most likely requir ed for additional specific functions in meiosis and fertilization. A telome re-binding protein complex from human sperm (hSTBP) has been isolated by de tergent treatment and was partially purified, hSTBP specifically binds doub le-stranded telomeric DNA and does not contain known somatic telomere prote ins TRF1, TRF2, and Ku. Surprisingly, the essential component of this compl ex has been identified as a specific variant of histone H2B. Indirect immun ofluorescence shows punctate localization of H2B in sperm nuclei, which in part coincides with telomeric DNA localization established by fluorescent i n situ hybridization. Anti-H2B antibodies block interactions of hSTBP with telomere DNA, and spH2B forms specific complex with this DNA in vitro, indi cating that this protein plays a role in telomere DNA recognition. We propo se that hSTBP participates in the membrane attachment of telomeres that may be important for ordered chromosome withdrawal after fertilization.