Gene regulation splicing - membrane bound vs secreted antibodies

Question 1

Where do secreted and membrane bound antibodies differ

Answer 1

At their C terminals. Hydrophilic amino acids present on the secreted antibodies cause they to be protruded from the membrane.

Question 2

What causes the with from bound to secreted?

Answer 2

There is a change in the length of B-lymphocyte mRNA at its 3’ end.

Question 3

How is the switch carried out?

Answer 3

1. unstimulated B cells produced from long mRNA
2. Upon antigen stimulation there is an increase in CstF
3. CstF binds poly A site.
4. mRNA is cleaved upstream of the splice before the last exon causing some of the last intron to be removed.
5. the coding sequence produces a shorter sequence and a secreted antibody is expressed.