The role of transcription factors in gene expression is to regulate when and how genes are turned on or off. These proteins bind to specific DNA sequences, facilitating the recruitment of the transcriptional machinery to initiate the synthesis of messenger RNA (mRNA) from DNA. Transcription factors can act as activators or repressors, influencing gene expression levels in response to various signals, such as hormones or environmental changes. Their precise regulation is essential for maintaining normal cellular function and responding to developmental cues.