Transcriptional

Transcriptional is an adjective relating to transcription, the process by which RNA is synthesized from a DNA template. In cells, transcriptional activity determines which genes are expressed, at what level, and in what context. The core process is carried out by RNA polymerases, which in prokaryotes operate with a sigma factor recognizing promoters, whereas eukaryotic transcription uses RNA polymerase II with general transcription factors to initiate transcription at core promoters, often modulated by enhancers, silencers, and chromatin state.

Transcriptional regulation refers to mechanisms that influence transcription initiation and, in some systems, elongation and termination. Activators and repressors bind specific DNA sequences to recruit or block the transcriptional machinery. Coactivators and corepressors bridge transcription factors to RNA polymerase II. Epigenetic marks, such as DNA methylation and histone modifications, alter chromatin accessibility and thereby the transcriptional potential of genes. Chromatin remodeling complexes can reposition nucleosomes to enable or restrict transcription.

Transcriptional profiling uses methods like RNA sequencing and microarrays to measure transcript abundance, producing transcriptomes that reveal gene expression patterns across tissues, developmental stages, or environmental conditions. These data support the construction of transcriptional regulatory networks that describe how genes influence each other’s expression. Transcriptional regulation is central to development, cell differentiation, responses to stimuli, and disease. Variability in transcriptional output among cells, termed transcriptional noise, also contributes to phenotypic diversity.