[Isolation and analysis of two cDNA-clones expressing the human lymphocyte expression library, inducing DNA-binding...

Two cDNA clones are sequenced which were isolated from human lymphocyte expression library using Southwestern (DNA-binding) screening with 32P-labeled Alu DNA in the presence of 100-fold excess of unbalanced poly (dI-dC). In one of the sequenced clones (vb22) an open reading frame (ORF) is detected, encoding protein with a new potential DNA-binding (zink-finger) domain, and DNA-binding activity of the protein is directly confirmed after its expression (as GST-fusion protein) in Escherichia coli. The other sequenced clone (wa12) is partially homologous to 15EST sequences present in GENBANK (April, 1996) and cloned from very different human tissues. Connection of these 15 overlapping GENBANK sequences resulted in a longer sequence covering wa12 and having ORF potentially encoding a new 10 kDa polypeptide without any apparent DNA-binding domains. This connected sequence as well as wa12 sequence having only 65 amino acids ORF are unrecognizable by computer software as the protein-coding regions, and we suppose that wa12 transcripts possess DNA-binding activity. Homopyrimidine blocks in RNA longer than 12 nucleotides are known to bind mirror duplex DNA sequences to form triplexes whose stability is comparable to that of protein-DNA complexes, and human promoters contain many such blocks.