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Little is known about the functions of DNA polymerase λ (Pol λ) recently identified in mammals. From the genomic sequence information of rice and Arabidopsis, we found that Pol λ may be the only member of the X-family in higher plants. We have succeeded in isolating the cDNA and recombinant protein of Pol λ in a higher plant, rice ( Oryza sativa L. cv. Nipponbare) ( OsPol λ). OsPol λ had activities of DNA polymerase, terminal deoxyribonucleotidyl transferase and deoxyribose phosphate lyase, a marker enzyme for base excision repair. It also interacted with rice proliferating cell nuclear antigen (OsPCNA) in a pull-down assay. OsPCNA increased the processivity of OsPol λ. Northern blot analysis showed that the level of OsPol λ expression correlated with cell proliferation in meristematic and meiotic tissues, and was induced by DNA-damaging treatments. These properties suggest that plant Pol λ is a DNA repair enzyme which functions in plant meristematic and meiotic tissues, and that it can substitute for Pol β and terminal deoxyribonucleotidyl transferase. [ABSTRACT FROM AUTHOR]

The biochemical and cell cycle-dependent properties of proliferating cell nuclear antigen (OsPCNA) and flap endonuclease-1 (OsFEN-1) were characterized from rice (Oryza sativa). OsPCNA was physically associated with OsFEN-1 and increased the flap-endonuclease activity of OsFEN-1 by 2.5-fold. Northern and Western blotting analysis revealed that OsPCNA and OsFEN-1 were present in meristematic tissues such as cultured cells, shoot apical meristem and root apical meristem. No expression was detected in the mature leaves, although they were exposed to UV. Both of these proteins were localized in the nuclei of the interphase cells including G1, S and G[sub 2], and in the nuclear region at telophase. The distribution patterns of plant PCNA and FEN-1 in meiotic cell progression were investigated using microsporocytes of lily (Lilium longiflorum cv. Hinomoto). During the leptotene to pachytene stages, PCNA and FEN-1 were localized in the nuclear region. The florescence gradually disappeared from diplotene to metaphase I. Interestingly, signals for PCNA formed 10-20 intense spots at leptotene. The number of spots decreased to 1-5 at zygotene and finally to I at pachytene. The roles of OsPCNA and OsFEN-1 in mitotic and meiotic cell cycles are discussed. [ABSTRACT FROM AUTHOR]

Abstract. Many kinds of bioactive peptides which might prevent lifestyle-related diseases are released from food proteins after enzymatic digestion. Inhibitory peptides for angiotensin I-converting enzyme (ACE) having anti-hypertensive effect have been isolated from enzymatic digests of various food proteins. LKPNM, which was isolated from the thermolysin digest of dried bonito was activated 8-fold by ACE itself and showed a prolonged effect after oral administration. Two vasorelaxing peptides, ovokinin and ovokinin(2-7), showing antihypertensive effect after oral administration were obtained from ovalbumin digests. We found that low molecular weight peptides derived from food proteins lowered serum cholesterol without increasing excretion of cholesterol and bile acids. An immunostimulating peptide isolated from an enzymatic digest of soybean protein prevented alopecia induced by cancer chemotherapy. [ABSTRACT FROM AUTHOR]