Chromatin immunoprecipitation (ChIP) and RT-PCR were performed to investigate activation of expression of a particular gene. X, Y and Z indicate ChIP with antibodies for specific proteins, and “RNA” shows gene expression at the indicated time points.

Based on the results, choose the option that correctly identifies the X, Y and Z proteins.

Correct option is A

Correct Answer
(a) X: H4K8Ac Y: TBP Z: H3K9Ac
Explanation
RNA expression starts after the appearance of TBP, indicating that TBP binding precedes transcription initiation. Histone acetylation marks appear earlier, consistent with chromatin opening before transcription. H4K8 acetylation is an early activation mark, while H3K9 acetylation correlates more closely with active transcription, matching the observed timing of X, Y, and Z.
Information Booster
• Transcription activation requires chromatin relaxation via histone acetylation
• TBP binding is a hallmark of pre-initiation complex formation
• H4 acetylation often precedes H3 acetylation during gene activation
• ChIP timing reveals the sequence of regulatory events
Additional Knowledge
Option (b) is incorrect because TBP binding does not precede chromatin modification. Option (c) misassigns TBP to a histone mark position, inconsistent with transcription timing. Option (d) reverses early and late acetylation events, which does not fit the RNA expression pattern shown.