Identification and characterization of a bovine sperm protein that binds specifically to single-stranded telomeric deoxyribonucleic acid

• Published in: Biology of reproduction Vol. 62; no. 2; pp. 340 - 346
• Main Authors: Kozik, A, Bradbury, E.M, Zalensky, A.O
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01-02-2000
• Subjects: Animals; binding sites; Biological and medical sciences; bulls; Cattle; Cell Nucleus - chemistry; Cross-Linking Reagents - chemistry; DNA; DNA, Single-Stranded - chemistry; DNA, Single-Stranded - drug effects; DNA, Single-Stranded - metabolism; DNA-binding proteins; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Immunoenzyme Techniques; In Vitro Techniques; Male; Mammalian male genital system; Molecular Weight; Morphology. Physiology; nucleotide sequences; Oligonucleotide Probes; Protein Binding; Proteins - chemistry; Proteins - metabolism; purification; repetitive sequences; single-stranded DNA; spermatozoa; Spermatozoa - chemistry; Spermatozoa - metabolism; Spermatozoa - ultrastructure; Telomere - metabolism; Telomere - ultrastructure; telomere binding proteins; telomeres; Ultraviolet Rays; Vertebrates: reproduction; Vertebrata; Spermatozoa; Mammalia; Ox; Single stranded DNA; Artiodactyla; Germinal cell; Telomere; Ungulata; Single strand DNA binding protein
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod62.2.340

Telomere DNA at the physical termini of chromosomes forms a single-stranded 3′ overhang. In lower eukaryotes, e.g., ciliated
protozoa, this DNA extension is capped by specific proteins that have been structurally and functionally characterized. Much
less is known about single-stranded telomere DNA-binding proteins in vertebrates. Here we describe a new protein from bovine
sperm designated bsSSTBP that specifically interacts with single-stranded (TTAGGG) N DNA. The bsSSTBP was extracted from nuclei by 0.6 M KCl. The native size of this protein, estimated by gel filtration, was
20–40 kDa. SDS-PAGE of the UV cross-linked complex between bsSSTBP and telomere DNA indicated that several polypeptides are
involved in complex formation. Bovine sSSTB had high specificity toward nucleotide sequence, since single nucleotide substitutions
in the (TTAGGG) 4 substrate suppressed binding. The minimal number of (TTAGGG) repeats required for binding of bsSSTBP was 3, and the protein
recognized linear but not folded DNA structures. We propose that the bsSSTBP participates in telomere-telomere interactions
and the telomere membrane localization observed in mature sperm. In mammals, somatic telomere-binding proteins are apparently
substituted by sperm-specific ones that may lead to a structural reorganization of telomere domains to fulfill functions important
during meiosis and fertilization.