lacZ encodes for b-galactosidase, a tetramer of 500 kD. The enzyme breaks lactose is cleaved into glucose and galactose. This enzyme also produces an important byproduct, b-1,6-allolactase.

TLS Online TPP Program

#Id: 1854

#Unit 3. Fundamental Processes

Class II promoters have two parts:

Core promoter having 4 elements

Upstream promoter element

TLS Online TPP Program

#Id: 1855

#Unit 3. Fundamental Processes

Start point, is the first base of mRNA to be A

• Initiator (Inr) is Py2CAPy5, where Py stands for any pyrimidine. The Inr is contained between positions -3 and +5.

• TATA box, usually located, 25 bp upstream in its location at -25

• The exception is in yeast, where the TATA box is more typically found at -90.

TLS Online TPP Program

#Id: 1856

#Unit 3. Fundamental Processes

Promoters that do not contain a TATA element are called TATA-less promoters. Surveys of promoter sequences suggest that 50% or more of promoters may be TATA-less.

TLS Online TPP Program

#Id: 1857

#Unit 3. Fundamental Processes

Constitutive active housekeeping genes and developmentally regulated genes have TATA-less promoters. 

 

TLS Online TPP Program

#Id: 1858

#Unit 3. Fundamental Processes

TATA less, Inr Less promoters uses Sp1 activator to position TBP with TAFs

TLS Online TPP Program

#Id: 1859

#Unit 3. Fundamental Processes

Sp1 (Mr  80,000) is a transcription activator for a large number of genes in higher eukaryotes. Its DNA binding site, the GC box consensus sequence GGGCGG.