An Interactive Introduction to Organismal and Molecular Biology, 2021

PROTEIN SYNTHESIS I: TRANSCRIPTION | 145
Various factors control how much a gene is transcribed. For instance, how tightly the DNA of the gene is
wound around its supporting proteins to form chromatin can affect a gene’s availability for transcription.
Proteins called transcription factors, however, play a particularly central role in regulating transcription.
These important proteins help determine which genes are active in each cell of your body.
Transcription Factors
What has to happen for a gene to be transcribed? The
enzyme RNA polymerase, which makes a new RNA molecule
from a DNA template, must attach to the DNA of the gene. It
attaches to a spot called the promoter.
The RNA polymerase can attach to the promoter only with
the help of proteins called general transcription factors.
They are part of the cell’s core transcription “toolkit,” needed
for the transcription of any gene.
More information
In bacteria, RNA polymerase
attaches right to the DNA of the
promoter. You can see how this
process works, and how it can be
regulated by transcription factors,
in the lac operon and trp operon
videos.
However, many transcription factors (including some of the coolest ones!) are not the general kind. Instead,
there is a large class of transcription factors that control the expression of specific, individual genes. For
instance, a transcription factor might activate only a set of genes needed in certain neurons.