The results of two sets of chromatin immunoprecipitation experiments on two cell types (1 and 2) are shown in the following simplified graphs for the same genomic region containing the first two exons of a gene. Antibodies against a transcription regulatory protein (X) or against a subunit of RNA polymerase II were used in the ChIP-seq experiments, as indicated. Do you think the protein is a transcriptional activator or repressor? The results from a parallel RNA-seq experiment are provided in the third graph. Which profile (a or b) in the graph would you expect to correspond to cell type 1?
A) Activator; profile a
B) Repressor; profile a
C) Activator; profile b
D) Repressor; profile b

Question

The results of two sets of chromatin immunoprecipitation experiments on two cell types (1 and 2) are shown in the following simplified graphs for the same genomic region containing the first two exons of a gene. Antibodies against a transcription regulatory protein (X) or against a subunit of RNA polymerase II were used in the ChIP-seq experiments, as indicated. Do you think the protein is a transcriptional activator or repressor? The results from a parallel RNA-seq experiment are provided in the third graph. Which profile (a or b) in the graph would you expect to correspond to cell type 1? 
A) Activator; profile a 
B) Repressor; profile a 
C) Activator; profile b 
D) Repressor; profile b

Quizplus · Accepted Answer

Protein X is enriched at the cis?-regulatory sequences in cell type 1, which corresponds to the lower RNA polymerase II occupancy over the gene, suggesting it is associated with repressed genes. Accordingly, RNA-seq results do not show significant peaks over exons in cell type 1 (profile b).

The Results of Two Sets of Chromatin Immunoprecipitation Experiments on Two