CSB428H1 : Article #3 Summary

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crimsonwombat705

24 Dec 2010

School

UTSG

Department

Cell and Systems Biology

Course

CSB428H1

Professor

U.Tepass

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Document Summary

Par-1 phosphorylates baz on two conserved serines, which is then bound by 14-3-3. This inhibits the baz/par-6/apkc complex by preventing baz oligomerization and binding to apkc. This excludes baz complex at lateral sides and also crb-sdt anchor baz complex apically. baz lacking par-1 phosphorylation/14-3-3 binding side for ectopic lateral complex. drosophila follicular epithelium surrounds germline and side facing germline is apical. 14-3-3 and par-1 is required for epithelial polarization par-1 null cells display uniform apkc and other apical protein around the cortex. 14-3-3/leo null cells mostly die. survivors show uniform cortex distribution of apical apkc, h - spectrin and basolateral marker-spectrin. a weaker leo mutant formed multiple layers of abnormal cells that failed to encapsulate germline. Par-6/apkc and h-spectrin was diffusely around entire cortex and formed abnormal aggregates. In a 14-3-3/+;leo/leo double mutant, cells lose cuboidal shape and baz, patj, arm is redistributed along the lateral and basal membranes.

Related Questions

7) Induction of Heat shock proteins such as HSP70 in Drosophila requires the binding of phosphorylated__________________ to specific ________________ and is an example of __________________ regulation of _________________

8) Transcription factors can bind to

a. Promoters

b. Enhancers

c. Silencers

d. Each other

e. Repressors

f. b+c

g. a+b+c+d

9.) Which of the following is considered a Local Histone Mobilization (circle all the correct ones and explain each)

a. Ejection

b. Phosphorylation

c. Sliding

d. Methylation

e. Unwrapping

What is the name of the complex that mediates this/these activit(y/ies)

5 A) Which of the following statements about apical and basolateral protein sorting is FALSE?

Transcytosis is a mechanism for the movement of basolaterally secreted proteins to the apical membrane.

Infection of epithelial cells with specific viral proteins has helped elucidate the mechanisms of polarized protein secretion.

GPI-linked proteins are sorted specifically to the apical membrane of most polarized epithelial cells.

Vesicles that bud from the trans-Golgi network travel specifically to the apical membrane.

5 B) How does lysosomal pH contribute to lysosomal protein sorting?

Lysosomal proteins only properly fold at the acidic pH found in the lysosome.

Acidic pH is required for fusion of clathrin-coated vesicles with the lysosomal membrane.

Clathrin/AP1 vesicles that travel to the lysosome have a high affinity for lysosomal membranes due to their low pH.

The mannose-6-phosphate receptor has altered affinity for M6P under acidic pH conditions.

sapphireeagle929

QUESTION 1:

(a)Examine the Figure below relating to the S.pombe cellcycle:

1) Describe the function of Cdc25 and Wee1and why deficit of Cdc25 or excess of Wee1 can cause G2arrest

2) b) Describe how deficit of Wee1 or excess ofCdc25 may result in abnormally small cells

(b) Theactivities of Wee1 tyrosine kinase and Cdc25 tyrosine phospatasedetermine the state of phosphorylation of tyrosine 15 in the Cdk1component of mitotic cyclin-Cdk complexes (MPF). When tyrosine 15is phosphorylated, M-Cdk is inactive; when tyrosine 15 is notphosphorylated, M-Cdk is active. Just as the activity of M-Cdkitself is controlled by phosphorylation, so too are the activitiesof Wee1 kinase and Cdc25 phosphatase. The regulation of thesevarious activities can be studied in extracts of frog oocytes. Insuch extracts Wee1 tyrosine kinase is active and Cdc25 tyrosinephosphatase is inactive. As a result M-Cdk is inactive because itsCdk1 component is phosphorylated on tyrosine 15. M-Cdk in theseextracts can be rapidly activated by addition of okadaic acid,which is a potent inhibitor of serine/threonine phosphatases. Usingantibodies specific for each component it is possible to examinetheir phosphorylation states by changes in mobility upon gelelectrophoresis.

(Phosphorylated proteins generally run slower than theirnon phosphorylated counterparts).

1) Based on theresults with okadaic acid, decide whether the active forms of Wee1and Cdc25 are phosphorylated or unphosphorylated. In the figureindicate the phosphorylated forms of Wee 1 and Cdc25 and label thearrows connecting their active and inactive forms to show whichtransitions are controlled by protein kinases and which by proteinphosphatases.

2) Are the proteinkinases and phosphatases that control Wee1 and Cdc25 specific forserine/threonine side chains or for tyrosine side chains? How doyou know?

3) How doesaddition of okadaic acid cause an increase in phosphorylation ofWee1 and Cdc25, but a decrease in phosphorylation ofCdk1?

4) If you assumethat Cdc25 and Wee1 are targets for phosphorylation by activeM-Cdk, can you explain how the appearance of a small amount ofactive M-Cdk would lead to its rapid and completeactivation?

silverotter963

CSB428H1 : Article #3 Summary

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