Question

Based on the known function of the following proteins, which, if lost, would likely not cause globalgene expression defects in eukaryotic cells?

	Basal transcriptional factors
	RNA polymerase
	Gal3
	Histones

Answer 1

Correct Option

Gal3 is a transcription regulator gene belong to family of Galactose inducible, glucose-repressible genes. It is required to induce transcription of Galactose inducible, glucose-repressible genes such as GAL1, GAL2, GAL7, GAL10, GAL80. Deletion or lost of GAL3 would not affect transcription of other genes (based on the known function).

Explanation for Incorrect Option

Basal Transcription Factors are the proteins require for initiation of transcription. In eukaryotes, following basal transcription factors are necessary for transcription.

• TFIIA - It stabilizes TATA Binding protein (TBP)
• TFIIB - recognizes and interacts with the core promoter element BRE in promoters
• TFIID – recognize and binds to TATA box, regulates TATA binding protein (TBP), TFIIB binds
• TFIIE - modulates activities of TFIIH
• TFIIF - functions in recruitment of RNA polymerase and also RNA polymerase - TBP and -TFIIB interactions
• TFIIH - It has a helicase activity; unwinds DNA at start point

Lost of these basal transcription factors affect the global gene transcription machinery. Because they bind or act at specific sites common to all gene (in promoter region).

RNA Polymerase

RNA Polymerase is an enzyme required for transcription of genes. They polymerize RNA strands from DNA template. RNA Polymerase is basic transcription apparatus. Without RNA polymerase, there would be no transcription of any gene. Polymerase does not differentiate genes to carry out transcription.

Histones

Histones are proteins found in eukaryotic nuclei and associate with DNA to condense genetic material and form nucleosome and chromatin. Histones are important for gene regulation. Histone modification such as methylation, acetylation, phosphorylation ubiquitylation, and sumoylation are important for gene regulation. Histone modification is carried out by histone modifier which may either increase or decrease transcription of genes. Specific gene transcription regulation is determined by type of histone modification. Without histones, there would be aberrant global gene expression. Also, it is critical for dynamic state of chromatin.