Molecular cloning of the silkworm p53r2-like gene

The p53R2 is a homologue of the small subunit of mammalian ribonucleotide reductase. In human, the transcription of p53R2 is induced clearly by active form of p53 and required for DNA synthesis during cell division and DNA repair. In this study, we have isolated and determined cDNA sequence for Bombyx mori p53R24ike (p53R2-L) protein. The Bmp53R2-like protein had high homology to the Hsp53R2, but had histidine residue at a position corresponding to Y241 of Hsp53R2, which is a key residue in discriminating human p53R2 and R2. Bmp53R2-L expressed strongly in the silk grand, gonad and blood cell, in which cell division occurs actively and DNA synthesis is required. The knockdown of the Bmp53R2-L in BmN4-SIDl led to a substantial arrest in Gl/S. This Gl/S arrest may be caused by the retardation of DNA synthesis due to the depletion of dNTPs in nucleus under the conditions of the knockdown of Bmp53R2-L. Thus, Bmp53R2-L is a functional homolog of human R2 rather than p53R2, and considered to be indispensable for DNA synthesis and cell cycle progression in a DNA damage independent manner.