Study On CDK Family Of Bombyx Mori

Cyclin-dependent protein kinases (CDK) are now widely recognized as key players at various checkpoint controls of the eukaryotic cell cycle. They belong to serine-threonine protein kinases, which require binding to corresponding cyclin protein for activity. In human cells, the CDK2, CDK4 and CDK6 controlled G,, while S and G2 were depended on CDK2. CDK1 was responsible for M phase. The CDKs also had other biological function:CDK5 had a prominent role in neuronal cell synapses. CDK7 was participated in regulating of transcription process. CDK8 appeared to switch off transcription by phosphorylating RNA polymeraseâ…¡C-terminal domain.We used Drosophila melanogaster and Tribolium castaneum's conserved domains as a probe to search for the Bombyx mori EST database, eight homologous ESTs were found. With the methods of DNAStar, Clustal X programms, these ESTs were classified to five groups: CDK4, CDK5, CDK7, CDK8, CDK9. Each had a conserved CDK domain and named CDK family of Bombyx mori. Besides, the CDK1 cDNA sequence had submitted to NCBI, while CDK2 cDNA sequence were predicted by bioinformatics methods, the other sequences were incomplete at 3'end.The cDNA sequences of CDK in Bombyx mori (CDK4, CDK5, CDK7, CDK8, CDK9) and the genomic sequences of CDK7, CDK9 were determined by RACE (Rapid Amplification of cDNA Ends) and bioinformatics analysis. Phylogenetic analysis of the predicted amino acid sequences of Bombyx mori, Drosophila melanogaster, Tribolium castaneum, Apis mellifera, Aedes aegypti, Homo sapiens, Rattus norvegicus by MEGA4, revealed that they were more similar to their corresponding counterparts from other organs including chordates than to each other. Homology analysis of the predicted amino acid sequences of Bombyx mori by Clustal X programs, the results showed that they all had a short conserved sequence, that is PSTAIRE sequence, but small difference was exited in these BmCDKs.At mRNA level, the expression pattern of BmCDKs was monitored by Real-time PCR, which including embryo development, thirteen tissues of the 6th day of 5th-instar larvae and infection by B. mori nucleopolyhedrovirus (BmNPV). Along with the development of embryo, the expression level at mRNA of BmCDK was decreasing until the sixth day, and then increasing slowly, and then increasing slowly, but CDK1 was different from other CDKs. Different ratios of the abundances of mRNA were observed in thirteen tissues of the 6th day of 5th-instar larvae, the highest expression level was in the middle silk glands, terminal silk glands, malpighian tubules, fat body, while low copy number was found in hemocyte, midgut.After infection by BmNPV, the expression of BmCDK mRNAs showed the similar expression pattern which associated with the replication of virion.