X Y and Z are three components of a regulatory system Both X

X, Y and Z are three components of a regulatory system. Both X and Y are transcription activators. How might X, Y and Z interact so as to form a sign sensitive delay element? Show graphically how such a sign sensitive delay element will effect gene expression While studying the regulation ol two genes A and B, a scientist finds the steady state concentration of B to be much more susceptible to fluctuations compared to A? Why do you think this is the case? The rate of transcription of a gene Y was found to be reduced in a mutant cell line. However while mapping the mutation, it was found to be present not in gene Y but in gene X, which is a transcriptional activator of gene Y. Write down three possible effects that the mutation might be having on X, so as to reduce the transcription of Y. What are two possible mechanisms by which signal transduction from a cytokine receptor may he stopped in the short term and in the long term? Although all activated cytokine receptors interact with SH2 domain-containing proteins, such as STATs, how is the specificity of the interactions ensured?

Solution

4.The two mechanisms by which signal transduction from a cytokine receptor may be stopped in the short term and long term are:

The binding of cytokines to cytokine activate JAKs first which increases the kinase activity of the JAKs.Activated JAKs phosphorylate tyrosine residues on the receptor that creates binding sites for STATs proteins possessing SH2 domains.SH2 domain containing STATs after binding to cytokine receptor are phosphorylated at the tyrosine residues by JAKs. STATs become activated and form hetero or homodimers. STATs then are and translocated to the nucleus of the cell and transcription of target genes is induced.From this we can conclude that activation of JAKs and the phosphorylation of tyrosine residues on SH2 domain of STATs by JAKs is required specifically for the interaction to take place.