Prolyl hydroxylase 

active at normal O2 levels, Hydroxylation of HIF-1 causes ubiquitinylation and degradation

TLS Online TPP Program

#Id: 6807

#Unit 3. Fundamental Processes

The precursor RNA for the siRNA pathway is a longer dsRNA. As a consequence of this different initial substrate, Drosha is not needed for the generation of siRNAs. Cleavage by Dicer is still required, however, and again generates a suitable 21- to 22-nucleotide RNA for incorporation into RISC.

TLS Online TPP Program

#Id: 6808

#Unit 3. Fundamental Processes

In plants, even miRNAs are generated by Dicer alone; it is not clear how they manage to forgo prior action of Drosha.

TLS Online TPP Program

#Id: 6809

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6810

#Unit 3. Fundamental Processes

RNA-dependent RNA polymerase (RdRP), an additional enzyme required in many cases of RNAi including centromeric silencing in fission yeast.

TLS Online TPP Program

#Id: 6811

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6812

#Unit 3. Fundamental Processes

RdRP has not yet been identified in mammalian cells, and high efficiency there likely results from the fact that slicing is catalytic— that is, each RISC can cleave several mRNAs.