4

DNA ^CAIł    Promotcr

SIIC

A) Binding 8c transcription

Natural GAI.4 protein

DNA ^I^^xA    Promotcr

Sltc    -■

No binding

DNA ^UxA    Promotcr

sile _

LexA

DNA-

binding

I Iybrid protein

u>

No binding

D) Binding &: transcription

DNA ^CAM    Promotcr

_    sile    _    _

FIGURĘ 10.02 Transcription Factors Have Two Independent Domains

A) One domain of a GAL4 transcription factor normally binds to tbe GAL4 DNA recognition sequence and anotber binds to tbe transcription apparatus. B) If the LexA sequence is substituted for tbe GAL4 site, tbe transcription factor does not recognize tbe DNA and no binding occurs. C) An artificial protein madę by combining a LexA binding domain with a GAL4 adivator domain will not recognize tbe GAL4 binding site, but D) will bind to tbe LexA recognition sequence and activate transcription. Tbus, tbe GAL4 activator domain acts independently of any particular recognition seguence. It works as long as it is held in close contact to tbe DNA.