Practice Questions

TLS Online TPP Program

#Question id: 2896

Different modification states of the residue Lys-9 on the tail of histone H3 could be interpreted to have different meanings. One example of how a histone modification can apparently influence a second modification present nearby is illustrated by the Drosophila HP1 protein. Which of the following statement is correct regarding this kind of epigenetic regulation?

#Unit 2. Cellular Organization

During metaphase, the HP1 protein binds in high concentration to the mitotic chromosomes, as they retain the essential “mark—namely, histone H3 methylation of lysine 9 (H3K9).
The dissociation of HP1 by the Aurora B kinase seems to be required for the attachment of the mitotic spindles to the centrosomes and the subsequent separation of sister chromatids during cytokinesis.
After the completion of mitosis, the phosphorylation of serine 10 is still retained because of Aurora B kinase activity, and HP1 dissociates from the chromosome to maintain the euchromatin state of chromosomes.
Loss of HP1 binding is associated with phosphorylation of the neighboring serine residue at position 10 of H3 which is mediated by a cell cycle kinase called Aurora B that becomes active only after the M phase of the cell cycle.