STEP EIGHT: CaMV & RT Caulimoviruses DS circular DNA w/ icosahedral capsid <> Retroviruses – RNA viruses Use CELLULAR DdRp for transcription Do NOT code for DdDp, but code for REVERSE TRANSCRIPTASE CaMV: 4 RNAs > 35S, RT, cell-cell movement prot., aphid transm. prot. 35S – one of the strongest eukaryotic promoters known Aphid transmission gene – taken out in genetic engineering THREE functions of RT 1. Make cDNA from RNA template 2. Degrade RNAs that are bound to DNA (RNase H activity) 3. Function as DdDp; use tRNA as a primer (met-tRNA in CaMV) Replication of CaMV 1. Cellular DdRp transcribe circular DNA into mRNA 2. mRNA has 13-NT long sequence complementary to met-tRNA 3. RT use met-tRNA as a primer & copy mRNA into cDNA 4. RNase H activity of RT degrade R (END REPEAT SEQUENCE) > tRNA bound to mRNA NOT degraded by RT 5. Now cDNA has R’ (complementary to R) > R of the other end of mRNA matches R’ > circularize & RT continues to make cDNA 6. Full (–) cDNA is made; has a nick where tRNA used to be bound
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