Histone methylation generally causes which effect on DNA transcription levels?

Histone methylation generally causes which effect on DNA transcription levels?

• A. Increases
• B. Has no effect on
• C. Increases transcription only after promoter methylation
• D. Decreases

Answer: (D)

Histone methylation changes how tightly DNA is packaged, which influences access to the transcription machinery. Repressive marks such as H3K9me3 and H3K27me3 recruit proteins that promote chromatin condensation, forming a closed state that RNA polymerase II and transcription factors can’t easily access. That reduced accessibility leads to lower transcription levels. (Note: some methylation marks can be associated with active transcription in specific contexts, but the overall tendency in many regions is repression, so transcription generally decreases.)

Histone methylation changes how tightly DNA is packaged, which influences access to the transcription machinery. Repressive marks such as H3K9me3 and H3K27me3 recruit proteins that promote chromatin condensation, forming a closed state that RNA polymerase II and transcription factors can’t easily access. That reduced accessibility leads to lower transcription levels. (Note: some methylation marks can be associated with active transcription in specific contexts, but the overall tendency in many regions is repression, so transcription generally decreases.)