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TLS Online TPP Program

#Id: 10551

The activation of RIPK1 kinase is a key decisive event that can initiate cell death by either apoptosis or necroptosis.

#Unit 4. Cell Communication and Cell Signaling #Apoptosis #Part B Pointers
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TLS Online TPP Program

#Id: 6504

#Unit 3. Fundamental Processes

Once bound to Pol II, Ptefb phosphorylates the serine residue at position 2 of the CTD repeats. That phosphorylation event correlates with elongation. In addition, P-TEFb phosphorylates and thereby activates another protein, called SPT5, itself an elongation factor. Finally, TAT-SF1, yet another elongation factor, is recruited by P-TEFb. Thus, P-TEFb stimulates elongation in three separate ways.
TLS Online TPP Program

#Id: 6755

#Unit 3. Fundamental Processes

Most mRNAs decay stochastically (like the decay of radioactive isotopes), and as a result mRNA stability is usually expressed as a half- life (t½).
TLS Online TPP Program

#Id: 6756

#Unit 3. Fundamental Processes

Method for determining mRNA half-lives.
RNA polymerase II transcription is shut down, either by a drug or a temperature shift in strains with a temperature sensitive mutation in a Pol II gene. The levels of specific mRNAs are determined by northern blot or RT-PCR at various times following shutdown.
TLS Online TPP Program

#Id: 6757

#Unit 3. Fundamental Processes

In E. coli the typical mRNA half-life is about 3 minutes, but half-lives of individual mRNAs may be as short as 20 seconds or as long as 90 minutes.  In budding yeast, mRNA half-lives range from 3 to 100 minutes, whereas in metazoans, half-lives range from minutes to hours, and in rare cases, even days.
TLS Online TPP Program

#Id: 6758

#Unit 3. Fundamental Processes

Degradation of bacterial mRNAs is initiated by removal of a pyrophosphate from the 5’ terminus. The monophosphorylated form stimulates the catalytic activity of an endonuclease RNase E
TLS Online TPP Program

#Id: 6759

#Unit 3. Fundamental Processes

PNPase a 3’ to 5’ exonucleases in E. coli, are unable to progress through double-stranded regions. Thus, the stem-loop structure at the 3’ end of many bacterial mRNAs protects the mRNA from direct 3’ attack.