TLS Online TPP Program

#Id: 6872

#Unit 3. Fundamental Processes

RNA-induced silencing complex (RISC/RITS) remodeling complexes to chromatin to form heterochromatin in telomeres.

The siRNA complex promotes methylation of histone H3K9 by the Clr4 methyltransferase (also known as KMT1, a homolog of Drosophila Su[Var]3–9). H3K9 methylation recruits the S. pombe homolog of HP1, Swi6.

TLS Online TPP Program

#Id: 6873

#Unit 3. Fundamental Processes

In human cells, the centromere- specific protein CENP-B is required to initiate modifications of histone H3 (deacetylation of K9 and K14, followed by methylation of K9) that trigger an association with HP1 that leads to the formation of heterochromatin in the region.

TLS Online TPP Program

#Id: 6874

#Unit 3. Fundamental Processes

Heterochromatin and RNAi are required to establish the human CenH3 homolog, CENP-A, at centromeres.

TLS Online TPP Program

#Id: 6875

#Unit 3. Fundamental Processes

Polycomb or Pc-G proteins do not initiate repression, but they are responsible for maintaining it.

TLS Online TPP Program

#Id: 6876

#Unit 3. Fundamental Processes

Most Polycomb proteins are subunits of one of two classes of multiprotein Polycomb repressive complexes: PRC1 and PRC2.

TLS Online TPP Program

#Id: 6877

#Unit 3. Fundamental Processes

The PRC2 complexes contain histone deacetylases that inhibit transcription. They also contain a subunit [E(z) in Drosophila, EZH2 in mammals] with a SET domain, which is the catalytic domain of several histone methyl transferases.