more questions about protein expression... - (Mar/22/2005 )

on mammalian cells:

# Methylation usually happens in CG islets. Does it occur most on C or G?


# Why are HGPRT, TK and APRT amplified selection markers while neomycine and hygromycin are not amplified selection markers? Why do we use HAT medium for TK marker?


Thanks.

hi
will cpg methylase methylates C on cg islands,
human DNA (cytosine 5) methyl transferase (Dnmt1) methylates C on cg island
dcm methylase CCWGG (but i'm not sure of which of the C)

as i found in neb catalog :
alu 1 methlase C in AGCT sequences
bamH1 methylase : C in GGATCC
dam methylase : GATC
EcoR1 methylase : GAATTC
Hae3 methylase : GGCC
hha 1 methylase : GCGC
hpa2 methylase : CCGG
msp1 methylase : CCGG
taq 1 methylase : TGCA