发信人: netbuggie (中原一点虫), 信区: Biology
标 题: Re: 大侠们, 请教一个问题.
发信站: The unknown SPACE (Sun Mar 4 02:49:12 2001), 站内信件

they are basically the same. the principle of run-on is that you first
isolate the nuclei and remove most of the proteins, but still keep the
RNA polymerase associated with nascent transcribed target gene. then
when you add NTP and p32 labeled UTP, the TXN will run on and then all
the product will be labeled. it allows mapping of the start point from
the size fractionated products.

run-off means that TXN occurs to in vitro DNA fragments, which are
typically restricted fragments with the start site already existed.
then you add all the stuff in the tube again. and let the TXN run off
to the end of the template. now there is mainly only one product.
from the size you can more accurately measure the start site position.
however, primer extension/ S1 nuclease protection are all effective
for such mapping purpose.

【 在 bigband (翻山过河走九州) 的大作中提到: 】
: LP要考QUALIFY了.
: 有个问题.
: 什么是nuclease run-on/run-off assay?
: 原理是什么? 什么应用?
: many thanks


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