Nucleic Acids to Proteins 3

Nucleic Acids to Proteins 3

• Primer tRNA binds to a complementary primary binding site
• A DNA sequence is synthesis (5' to 3')
• The viral R and Ur regions at the 5' end are removed by reverse transcriptase H
• The newly synthesised DNA segment makes a jump to the 3' end of the viral RNA and binds to the R region by base pairing
• A long DNA sequence complementary to the viral RNA strand is then synthesised
• The viral U3 and R regions are removed by reverse transcriptase H leaving the PP region
• A complementary DNA sequence (5' to 3') is then synthesised
• The tRNA primer is removed and second jump of the cDNA to the 3' end takes place
• This is followed by the synthesis of a complementary DNA sequence

• Gemcitabine is used to treat various types of cancers such as pancreatic cancer, breast cancer, non-small cell lung cancer and bladder cancer
• Gemcitabine has two active metabolites
  • gemcitabine diphosphate
  • gemcitabine triphosphate
• The diphosphate inhibits ribonucleotide reductase, an enzyme that converts ribonucleotides into 2'-deoxyribonucleotides, inhibiting DNA synthesis
• The triphosphate causes apoptosis through inhibition of DNA elongation

• Gemcitabine triphosphate takes part in DNA synthesis
• Upon incorporation, it only allows the addition of one nucleotide after Gemcitabine, after which further DNA elongation is inhibited
• Gemcitabine diphosphate binds irreversibly to the ribonucleotide reductase and inhibits its activity
• This results in the inhibition of the synthesis of 2'-deoxyribonucleotides and so DNA synthesis is stopped