Identification of two novel human putative serine/threonine kinases, VRK1 and VRK2, with structural similarity to vaccinia virus B1R kinase.

A cDNA library enriched for human fetal-specific liver genes was constructed by suppressive subtractive hybridization. EST fls223 generated from this library was found to represent a novel putative serine/threonine (Ser/Thr) kinase. A full-length clone isolated for this gene encodes a protein of 396 amino acids. The amino acid sequence has 40% identity over 305 amino acids with the B1R Ser/Thr protein kinase of vaccinia virus. This gene has therefore been named VRK1 (vaccinia virus B1R kinase related kinase). VRK1 was also found to have sequence identity (62.0% over 481 nucleotides) to a database EST. A full-length clone for this EST was isolated and sequenced. Conceptual translation predicts a protein of 508 amino acids that, like VRK1, has similarity to B1R kinase (38.7% identity over 300 amino acids). This gene has been named VRK2. Comparison of VRK1 with VRK2 indicates that they encode structurally related putative Ser/Thr protein kinases. Northern analysis shows that expression of both genes is widespread and elevated in highly proliferative cells, such as testis, thymus, and fetal liver. B1R kinase is reported to be essential for DNA replication of vaccinia virus. The similarity of VRK1 and VRK2 to B1R indicates that these genes may have similar functions.