Overexpression of heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1, es
pecially of B1 has been reported as a useful marker to detect cancers in ea
rly stage, although the biological reason is not clear. A2/B1 proteins were
previously reported to bind telomeric DNA repeats. Alternative splicing of
A2/B1 gene produces abundant A2, less abundant B1, and testis-specific min
or isoforms B0a and B0b. In this study, B1 and B0b that have the N-terminal
12 amino acid insertion were suggested to have higher affinities to telome
ric single-stranded DNA (ssDNA) than A2 and B0a. Kinetic analyses using pur
ified B1 and B0b indicated that they interact dynamically with a single arr
ay of telomeric repeats. Furthermore, functional assays demonstrated that B
1 and B0b bind with telomeric repeats in a tandem fashion and protect them
from a nuclease and promote telomerase activity. A2/B1 proteins, especially
B1 and B0b, may function as telomeric ssDNA-binding proteins in cancer and
reproductive cells, (C) 2001 Academic Press.