Basic Transcription Part 4 Flashcards
1
Q
Anti termination by N
A
- can cause anti termination at both rho-dependent and independent terminators
- binds to hairpin to prevent its formation
2
Q
site to the right of cro allows
A
-polymerase to ignore terminator and enter the delayed early genes
3
Q
Q utilization site (qut site)
A
- overlaps late promoter PR’
4
Q
in absence of Q
A
- RNA polymerase pauses for several seconds at qut site
- then transcribes to the terminator and stops late transcription
5
Q
In presence of Q
A
- Q recognized paused complex and binds qut site
- Q inhibits hairpin formation
- Q then binds polymerase and causes it to resume transcription and ignore terminator and continue into late genes
6
Q
to progress from immediate early to delayed early genes
A
- requires anti termination by N
7
Q
to progress from delayed early genes to late genes
A
- requires anti termination by Q
- at qut site just downstream of Q
- Q is a delayed early gene
8
Q
cI
A
- encodes lambda repressor protein
9
Q
2 promoters control the cI gene
A
- PRM
- PRE
10
Q
repressor maintenance
A
- PRM
- used during lysogeny to provide continual supply of repressor to maintain lysogenic state
- requires the product of its own product for activity - auto regulation
11
Q
why PRM cannot be be used to establish lysogeny
A
- because no repressor present to activate it
- instead PRE is used
12
Q
PRE
A
- promoter establishment
- located to the right of PR and cro
- directs transcription leftward through cro and then through cI
- allows cI expression before any repressor is available
13
Q
PRE transcription
A
- cro usually transcribed rightward from PR
14
Q
leftward transcription from PRE
A
- produces antisense product of cro
- sense product of cI
15
Q
antisense RNA
A
- helps establish lysogen by binding to cro mRNA
- cannot be translated
16
Q
promoting lysogeny
A
- Cro works against lysogeny
- blocking cro promotes lysogeny
17
Q
CII
A
- promotes transcription from a leftward promoter (anti-Q) within Q
18
Q
cII promotes transcription from a leftward promoter (anti-Q) within Q
A
- promotes Q antisense RNA - blocks production of Q
19
Q
What is Q required for
A
- late transcription in lytic phase
- interfering with its synthesis favors lysogeny
20
Q
cII function
A
- can stimulate polymerase to bind only PRE, P1, and anti-Q
- but not other promoters
21
Q
P1
A
- promoter for integrase for lysogeny
22
Q
PRE area
A
- -10 and -35 boxes with no similarities to consensus
23
Q
cII interaction RNA pol
A
- cII required for transcription for transcription
- RNA pol can’t bind alone
- cII can’t bind alone
- both proteins can bind and form a stable complex around the promoter
24
Q
how do cII and RNA pol bind
A
- bind cooperatively to the promoter on opposite sides of the helix
25
cIII
- prevents destruction of cII by proteases in the cell (key stop for deciding between lysis or lysogeny)
- works with cII to establish lysogeny by activating PE and P1
26
lambda repressor binds where to do what
- to both OR and OL
| - to turn off further early transcription, interfering with the lytic cycle
27
why is turning off cro important
- stimulate own synthesis (lambda repressor) by activating PRM
- allows pol to bind further transcribing the repressor which inhibits transcription from left and right
28
OR division
- divided into three parts
- OR1, OR2, and OR3
- each can bind repressor
29
OR controls
- leftward transcription of cI
| - rightward transcription of cro
30
repressor binds most tightly to
- OR1
- then OR2
- and least tightly to OR3
31
how many repressor binding sites in each operator
3
32
repressor is a
- dimer
| - each subunit has 2 domains
33
first domain of repressor
- DNA binding
34
second domain of repressor
- involved in repressor-repressor interactions
35
repressor dimers bound to both OR1 and O2 close to the binding site for RNA pol at PRM
- inhibit RNA pol from binding to PR but help bring in pol to bind to PRM
- prevent transcription from PRE
36
how the repressors prevent transcription from PRE
- by blocking cII and cIII transcription from PR and PL
37
what are cII and cIII required for
- required for transcription from PRE
38
during lysogeny lambda repressor does what
- represses transcription from PL and PR
| - stimulates transcription from PRM
39
polymerase-repressor interactions
- required for activation of transcription from PRM
40
activation interaction involves
- sigma factor not alpha
41
lambda repressor interacts with which region of sigma factor
- region 4
| - substitutes for weakly recognized -35 box
42
maintaining lysogeny
- once lysogeny established, a small amount of repressor is required to maintain it
- cII and cIII disappear
43
race between cro and cI
- if cI wins, lysogeny results
| - cro wins, lytic cycle results
44
cI wins
- cro binds first to OR3 (has highest affinity for)
| - cI binds 1, 2, 3
45
cro wins
- if cro binds OR3 prevents cI binding
- cI transcription from PRM stops
- OR3 overlaps PRM
- cro represses PRM
46
cII level
- determines lysis or lysogeny
47
cII will
- activate PRE and help turn on lysogeny program
| - work against lysis by making anti-sense cro RNA
48
in a rich medium
- high protease concentration
- not enough cIII to protect cII
- lysis
49
most important determinant in lysis versus lysogeny
- concentration of cII
50
switch from lysogeny to lysis
- mutagenic chemicals can do it
| - SOS response
51
immunity region
- contains cI, OR, OL, and cro
- lysogen are immune to superinfection by a phage with the same control region
- lambda repressor represses new phage DNA from infecting the cell
