GPCR regulation is additionally mediated by gene transcription factors. CREs typically regulate gene transcription by binding to transcription factors. Methylation impairs DNA transcription and expression of the MGMT gene. Glucocorticoids may also inhibit the rates of POMC gene transcription and peptide synthesis. HTT also facilitates vesicular transport and synaptic transmission and controls neuronal gene transcription. Growth factors initiate signal transduction pathways, which lead to activation of transcription factors. The outcome can be activation of transcription or repression of a gene. These include binding to proteins involved in dephosphorylation pathways and blocking DNA binding transcription factors. HMGB1 supports transcription of many genes in interactions with many transcription factors. These complexes function independently for transcription and replication related processes. This map is controlled by secreted signaling proteins and downstream transcription factors. Histone ubiquitination alters chromatin structure and allows the access of enzymes involved in transcription. Cofactors are proteins that modulate the effects of transcription factors. This allows for promoter DNA accessibility to various proteins, such as transcription factors. It can be transcribed with the symbol (a lowered ) in narrow transcription.