|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1995 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1994 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Cellular level of ornithine decarboxylase (ODC) is under negative feedback regulation by its products putrescine and polyamines. We elucidated previously that polyamine-induced regulatory protein, antizyme (AZ), binds with ODC,destabilizing it. We also found another possible regulatory protein, antizyme inhibitor (AI), which is of similar size with ODC and binds with AZ with higher affinity than ODC.Following results were obtained by the present study.
1. Sequence analysis of AI cDNA cloned from rat heart cDNA library revealed that AI is a protein consisting of 448 amino acids, which is highly homologous (47.5 percent identity) to, but clearly distinct from rat ODC,lacking PEST containing C-terminal region essential for rapid degradation. This result excluded the possibility that AI is some post-translational derivative of ODC.
2. Examination of the effect of forced expression of transfected AI is under way right now with no firm result yet.
3. AZ cDNA was isolated from the liver of Xenopus laevis and its sequence determined. The frog AZ cDNA had 63 percent homology with rat AZ cDNA and had a similar structure with rat cDNA that necessitates polyamine-induced ribosomal frameshifting for its translation. Although polysmines caused mild suppression of ODC in a protozoa Tetrahymena, the rate of ODC degradation was not affected by polyamines and ODC inhibitory factor, of either free or complexed form, was not detected in the cell extract, suggesting that repression of ODC synthesis alone is responsible for the polyamine-caused suppression of ODC in the protozoan cells.