Week 5

Question 2

role of RecBCD
- role of subunits B,C,D

Answer 2

forms recombinogenic end

B– 3-5 helicase/nuclease
C– 5-3 prime helicase
D– recognizes Chi site– stops 3 prime tail digestion

Question 3

describe the role of RecA in cross-strand exchange (homologous recombination)

Answer 3

facilitates strand invasion— leads to branch migration
- binds selectively to DNA junctions as a tetramer

Question 4

describe the role of RuvB in cross-strand strange

Answer 4

• facilitates branch migration
• binds to DNA as 2 hexamer complexes
  – helicase activity (ATP required) to spool DNA through junction– extends heteroduplex region

Question 5

Role of RuvC in cross-strand exchange
- what kind of cleavage (what endonuclease)?
- what is the yeast (euk.) equivalent of RuvC?

Answer 5

structure-selective nuclease targeted to DNA junctions
—capable of 4 way junction cleavage– mediated by T4 endonuclease VII

• YEN1 enzyme does this in yeast

Question 6

in what mechanisms do we see formation of holliday junctions and subsequent DNA interaction

Answer 6

1. DNA strand invasion during meiosis crossing-over event
2. DNA damage repair i.e. double stranded break
3. DNA replication i.e. rescuing of the replication fork (repl. fork broken due to ss nick ahead of it.)