RNA in us, versus viruses

[ilzmastr]

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Why does RNA only have a half-life of 30 minutes in eukaryotes, while viruses may store all of their genetic information as RNA and (presumably) last much longer than 30 minutes?

Is something breaking down the RNA in eukaryotes? And what about in prokaryotes?

 

[blueshockey]

Eukaryotic RNA is distinct from prokaryotic RNA due to the presence of 5' caps as well as a polyA tail, which prevents the eukaryotic RNA from being degraded in the cell (it will happen eventually anyway). Prokaryotic RNA doesn't need to worry about capping or the tail because it's not nearly as likely to be degraded. That help?

 

[N1st]

Also an individual virus wouldn't necessary have to survive very long, because they reproduce often.

 

[ilzmastr]

Thanks, ya helps a bit.
But just a heads up, I found out that prokaryotic mRNA is degraded much quicker than in eukaryotes.

http://en.wikipedia.org/wiki/Messenger_RNA#Prokaryotic_mRNA_degradation

I guess the degradation is all about regulating gene expression, allowing genes to be turned on and off chronologically, not just spatially in the body. And since translation is happening all the time, transcription has to yield a transient product, otherwise cells would never be able to change.
While in viruses I'd suppose no regulation is necessary and that the RNA is always on and never degraded, but how does it prevent its own degradation when its in a new foreign cell?