FoundationalConceptsNeuroscience

Transcription-factor proteins RNA polymerase

% { Gene: protein-coding

( region of DNA

DNA

Nee al,

Regulatory region i Xv Gene transcription

of DNA begins here

Figure 10.1. Transcription factor proteins bind to regulatory regions of DNA
and modulate the readout of genes. The enzyme RNA polymerase catalyzes
the synthesis of RNA transcripts using DNA as the template.

A surprising recent discovery is that while only a small part (<3
percent) of the human genome codes for functional protein, most
(>85 percent) of the genome is transcribed into RNAs of various kinds.
These RNAs that are not translated into protein appear to be crucially
involved in the regulation of gene expression, in ways that are not yet
understood. Referencing the famous and mysterious dark matter and
dark energy of cosmology, some folks have referred to the >97 percent
of the human genome that does not code for functional protein as
the dark matter of the DNA. In the 1970s, when these nontranslated
sequences first began to be characterized, the phrase “junk DNA”
was often used. However, because cells spend a great deal of energy
transcribing and manipulating these nontranslated sequences, they
are clearly playing important roles and are certainly not junk. Figur-
ing out the roles of this regulatory RNA is one of the most exciting
projects of contemporary molecular biology.