This question concerns the proteins involved in transcription and RNA modificati
ID: 208390 • Letter: T
Question
This question concerns the proteins involved in transcription and RNA modification.
a. Indicate two proteins in either prokaryotes or eukaryotes that act as a helicase to separate two DNA strands during transcription.
b. Indicate one protein in prokaryotes that acts as a helicase to separate RNA from DNA during transcription.
c. Indicate three molecules in eukaryotes that function during RNA modification as ribozymes.
d. Indicate one protein in prokaryotes that acts as a transcription factor.
e. Indicate one enzyme in eukaryotes that synthesizes a long string of identical RNA nucleotides but does not use a template DNA strand for RNA synthesis.
Explanation / Answer
Answer a. Helicases can be classified in six superfamilies. Two proteins that act as helicases in either prokaryotes or eukaryotes are.
1. UvrD, also known as DNA helicase II in gram-negative bacteria is an example of DNA helicases.
2. DEAD-box RNA helicases are superfamily type II helicases and as the name suggests are RNA helicases. They are highly conserved and can be found in most prokaryotes or eukaryotes.
Answer b. Rho factor is a protein that is involved in separating RNA-DNA hybrids in prokaryotes.
Answer c. Three molecules in eukaryotes that function during RNA modification as ribozymes
1. Ribonuclease P, also known as RNaseP is a known ribozyme in human cells as well as in archaea and bacteria
2. Twister ribozyme is also a known ribozyme that functions during RNA modification. It is also present in bacteria, fungi, plants, and animals.
3. Hammerhead ribozyme named so because of the resemblance of its secondary structure to the hammerhead shark. This molecule catalyzes reversible cleavage and joining reactions at specific sites in an RNA molecule and is observed to be present across the species ranging from bacteria to humans.
Answer d. TAL (transcription activator-like) effectors are proteins secreted by Xanthomonas bacteria. This protein binds to the promoter sequences in the host plant and in turn, activates the expression of plant genes that help in spreading bacterial infection.
Answer e. RNA-dependent RNA polymerase (RdRP) are the enzymes found in several eukaryotes that do not require a DNA template to carry out its function. As the name suggests it requires an RNA template to do its job.
Furthur, recent scientific publications have shown a class of RNA polymerases that are template independent and do not require either a DNA or an RNA template for its functioning. One such example is CTP:(ATP) tRNA nucleotidyltransferase.
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