| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The biogenesis of eucaryotic ribosomes requires an equimolar accumulation of four RNAs and over 70 different ribosomal protein molecules. This stoichiometry is maintained over a wide range of physiological conditions by coordinate regulation. We intended to study the structure of the genes for individual ribosomal proteins to investigate the control mechanisms.
Clones containing cDNA inserts complementary to the mRNAs encoding ribosomal proteins S11, S17, S26, L5, L7a, L27, L30, L31, L35a, and L37a were isolated by hybrid-selected translation from the cDNA library made for 8-9 s poly(A)-RNA from regenerating rat liver. The nucleotide sequences of these cDNA were determined. The structures of these proteins were infered from the nucleotide sequences to confirm the identity of these clones.
Using the recombinat DNAs, we found that the relative abundance of the mRNAs of these proteins increased after partial hepatectomy. Their maximal level was about twice that of normal rat liver, and was achieved 12-18 h after the operation. The abundance decreased near to the normal level after 48 h.
The rat ribosomal protein genes comprise multigene families which contain 15-20 memberes as shown by the Southern blot anaylyses using the cDNAs as probes. We isolated many independent clones of S11,L27,and L35a from a rat genomic library. Analysis of the restiction sites showed that all of them lacked the intervening seguences. Thermal stability of the hybrid molecules beween these genes and the cDNAs indicated that the nucleotide sequences of these genes had various similarities to the the sequences of the cDNAs. These genes lacked the intervening sequence, they contained (A)-rich tracts, and they were flanked by direct repeats. Thus, the ribosomal protein gene families were proven to comprise mostly processed pseudogenes.
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