Cis and Trans Factors

exam 3, bio 219, WVU fall '26

Cis factors: definition

built into DNA, determines what’s transcribed

Trans factors: definition

built in another location (proteins)

Promoters

cis

TATA box

cis

Core promoter

closest to transcription start site

Proximal promoter

medial distance from transcription start site

Distal promoter

furthest from transcription start site

Enhancer

cis factor, binds activator

Silencer

cis factor, binds repressors

Activator

trans factor

Repressor

trans factor

Effector

bind to an activator, turns it on via allostery

TF2D

binds to TATA box

TF2H

aids helicase and RNA polymerase

Regulatory transcription factors: function

influences the stability of RNA poly binding

Trans factors determine __

when, where, and how much transcript is made

Positive activation

activator + effector = more transcription

Positive repression

activator + effector = less transcription

Negative activation

repressor + effector = more transcription

Negative repression

repressor + effector = less transcription