Question

Question 5 (Fill in the tables): This question is asking about the Substrate/Protein process in Mitosis.

Please answer Question number 5:

* Give the name of the Kinase associated with the Substrate/Protein.

*Then on the 3rd column "Consequence of phosphorylation", please fill in and describe what happens when the Substrate/Proteins are phosphorylated.

Question 6 (Short answer essay): This question is asking about the signaling pathway of the formation of syncytia.

Please answer Question number 6:

* Simply answer by short essay format.

* Draw a diagram describing the process.

Phosphorylation in mitosis 5. Phosphorylation regulates many steps in mitosis. For each of the factors given, indicate the kinase that phosphorylates this substrate and the consequence for phosphorylation. Substrate Kinase Consequence of phosphorylation Cohesin Condensin Ndc80 Lamins Separase APC/C - Cdc20 APC/C - Cdh1 6. A syncytium is a "cell" that contains more than one nucleus; examples are a skeletal muscle fiber and a blastula of a fly embryo. These two types of syncyti embryo. These two types of syncytia arise by very different pathways. What two mechanisms can you envision that could lead to formation of a syncytia?

Answer 1

Question 5

Substrate	Kinase	Consequence of phosphorylation
Cohesin	PLK1	Before the start of Anaphase, the sister chromatids are held in place by the cohesin complxes. In late metaphase, PLK1 phosphorylates cohesin leading to the dissociation of cohesins from the arms of the chromosomes. As a result, this promotes the splitting of the centromere and the separation of the sister chromatids during anaphase.
Condensin	CDC2	In vitro experiments have shown that CDC2 phosphorylation of condensin activates it.
NDC80	Ipl1/Aurora B kinase	In vitro experiments have shown that phosphorylation of the Ndc80 kinetochore protein by the Ipl1/Aurora B kinase results in a reduction of its microtubule binding activity.
Lamins	Mitosis-Promoting Factor (MPF)	During the duration of mitosis, lamins are phosphorylated by Mitosis-Promoting Factor (MPF). This leads to the disassembly of the lamina and the nuclear envelope. As a result of this, the chromosomes can condense easily and the DNA replication can take place.
Separase	CDK1-cyclin B1	CDK1-cyclin b1 phosphorylates separase at Ser-1126 and this leads to an increase in the tendency of securin free separase to aggregate and become inactive. So this is basically a kind of an inhibitory phosphorylation for separase that leads to the loss of its activity.
APC/C-CDC20	CDK1	CDK1 phosphorylation leads to the binding of APC/C to CDC20. This usually happens when the levels of CDK1 are high and as a result of formation of APC/C-CDC20 complex and its activation, the cell prepares to enter anaphase and eventually exit mitosis.
APC/C-CDH1	CDK	At the end of the G1 phase, APC/C-CDH1 is inhibited by the CDK phosphorylation of CDH1. Therefore, this is also an example of inhibitory phosphorylation.