Nuclease protection assays - which RNAse?

[James Wheeler]

I am using zebrafish specific RNA probes in a Ribonuclease 
Protection Assay (all Ambion products). However, I would also like 
to use my probes on other fish species. I remember reading 
somewhere that for cross-specific probes it is better to use RNAse 
T1 instead of RNAse A. Is this true and why? Does anybody have 
any idea of how many mismatches would be tolerated during the 
hybridisation before a 'cut' would be made breaking the probe 
mRNA duplex giving fragments not of expected size.  

Many thanks,

James

School of Biological Sciences
Royal Holloway, University of London
Egham
Surrey
TW20 0EX

j.wheeler at rhul.ac.uk