Basic Transcription Part 4 Flashcards Preview

GN 421 > Basic Transcription Part 4 > Flashcards

Flashcards in Basic Transcription Part 4 Deck (51):
1

Anti termination by N

- can cause anti termination at both rho-dependent and independent terminators
- binds to hairpin to prevent its formation

2

site to the right of cro allows

-polymerase to ignore terminator and enter the delayed early genes

3

Q utilization site (qut site)

- overlaps late promoter PR'

4

in absence of Q

- RNA polymerase pauses for several seconds at qut site
- then transcribes to the terminator and stops late transcription

5

In presence of Q

- 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

to progress from immediate early to delayed early genes

- requires anti termination by N

7

to progress from delayed early genes to late genes

- requires anti termination by Q
- at qut site just downstream of Q
- Q is a delayed early gene

8

cI

- encodes lambda repressor protein

9

2 promoters control the cI gene

- PRM
- PRE

10

repressor maintenance

- 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

why PRM cannot be be used to establish lysogeny

- because no repressor present to activate it
- instead PRE is used

12

PRE

- 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

PRE transcription

- cro usually transcribed rightward from PR

14

leftward transcription from PRE

- produces antisense product of cro
- sense product of cI

15

antisense RNA

- helps establish lysogen by binding to cro mRNA
- cannot be translated

16

promoting lysogeny

- Cro works against lysogeny
- blocking cro promotes lysogeny

17

CII

- promotes transcription from a leftward promoter (anti-Q) within Q

18

cII promotes transcription from a leftward promoter (anti-Q) within Q

- promotes Q antisense RNA - blocks production of Q

19

What is Q required for

- late transcription in lytic phase
- interfering with its synthesis favors lysogeny

20

cII function

- can stimulate polymerase to bind only PRE, P1, and anti-Q
- but not other promoters

21

P1

- promoter for integrase for lysogeny

22

PRE area

- -10 and -35 boxes with no similarities to consensus

23

cII interaction RNA pol

- 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

how do cII and RNA pol bind

- 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