Lecture 3 - Exam 3 Flashcards
Do you remember the central dogma of biology? What is it?
1) Transcription (in the nucleus)
2) Processing (in the nucleus)
3) Transport out of nucleus
4) Translation
5) Protein folding and modification
6) Carry out function
When we discuss morpholino oligonucleotides, there is a part where we can use MO to splice out exons. Remember that spliceosomes are important in this process. What is the assembly process of a spliceosome?
1) U1 SnRNP binds to the 5’ splice site of pre-mRNA
2) U2 snRNP binds to the branch point by similar complimentary pairing between branchpoint DNA and U2.
3) Preformed U4/U6 and U5 snRNPs join the complex.
Discuss oocytes and their mRNA.
The oocyte (egg) often makes and stores mRNAs and proteins that are prevented from being translated until after fertilization (ion waves).
In many species, like sea urchins, frogs and fish, early cell division is controlled by proteins made from stored mRNA.
Also, mRNA is often stored in specific regions of the egg that will be necessary to specify cell fate in specific territories of the developing embryo.
Discuss the maternal contributions to DNA replication in the zebrafish blastula.
During oogenesis, the oocyte often makes and stores mRNAs and proteins that will be used after fertilization.
These will be activated by ion signals. Used for cleavage/DNA replication etc. as well as getting development started. These maternal contributions are often called “maternal factors.”
Remember noncoding micro RNAs (miRNAs)? What are miRNA genes?
miRNA genes are transcribed to yield primary transcripts (pri-miRNAs) that contain hairpin structures.
Describe the regulation of translation by miRNAs. (Long!!)
miRNA genes are transcribed to yield primary transcripts (pri-mRNAs) that contain hairpin structures.
Pre-miRNAs are sequentially cleaved by the nucleases Drosha and Dicer to yield double-stranded miRNAs of approximately 22 nucleotides.
miRNAs associate with the RISC complex in which the two strands of the miRNA are unwound.
The miRNA then targets RISC to the 3’ untranslated region of an mRNA. This hybridization leads to the inhibition of translation, deadenylation, and mRNA degradation.
Inhibition of translation may result from interference with the activity of eIF4A and inhibition of ribosome scanning.
What is the action of chaperones during translation?
Chaperones bind to the amino (N) terminal portion of the nascent polypeptide chain, stabilizing it in an unfolded configuration until synthesis of the polypeptide is completed.
The completed protein is the released from the ribosome and is able to fold into its correct three-dimensional conformation.
Chaperones of the Hsp70 family do what?
Bind to and stabilize unfolded polypeptide chains during translation.
The unfolded polypeptide is then transferred to a member of the chaperonin family, within which protein folding takes place. ATP hydrolysis is required for release of the unfolded polypeptide from Hsp70 as well as for folding within the chaperonin.
Describe the action of protein disulfide isomerase.
Protein disulfide isomerase (PDI) catalyzes the formation of disulfide bonds. Critical for tertiary and quaternary structure.
The Ras proteins alternate between what two forms?
What is the major effect of one form versus the other?
Active GTP-bound and inactive GDP-bound forms.
The major effect of GTP binding versus GDP binding is alteration of the conformation of two regions of the molecule, designated the switch I and switch II regions.
