Lecture 41: Protein Synthesis Control/Cancer Flashcards
Mitochondrial protein translocation process
- OMM receptor binds pre-seq. helix
- TOM complex forms; OMM/IMM channels align
- Protein threads through to matrix
- Mitochondrial matrix chaperones mediate folding, translocation
Mitochondrial localization sequence
Pre-sequence, amphiphilic helix w/ one hydrophobic side one charged side
PDH defect clinical case
High lactate due to PDH E1alpha not being imported efficiently into mitochondria; Pro substitution mutation disrupts pre-sequence localization helix for receptor
Nucleus selective diffusion barrier
Small things pass thru nuclear membrane, larger proteins require active transport. Mediated by Nup (nucleoporin) proteins e.g. Phe-Gly (FG) Nups
Nuclear Localization Signal
Lys-Lys-Lys-Arg-Lys
NLS binds cytoplasmic importins for transport into nucleus via nuclear pores
Importins/exportins
Carriers that mediate transport into/out of the nucleus by binding w/ Nups in nuclear pores
Nuclear lamina
Thick layer of intermediate filaments (nuclear lamins) that associate, not attach to, nuclear envelope. Maintains nuclear structure and stabilizes nuclear pore complexes
Hutchison-Gilford Progeria Syndrome
Nuclear lamina defect due to truncated modified progerin attaching nuclear lamina to envelope. Inhibits import/export from nucleus. Treatment w/ farnesyl transferase inhibitors (farnesyl group is what attaches mutant protein to envelope, normally cleaved)
Restriction endonucleases (enzymes)
Perform seq-specific cleavage of 4, 6, or 8 bases at double strand palindromic sites. Require perfect base pairing to function
Restriction enzyme sites
- Blunt ends (cleavage in middle)
- Sticky ends (leaves 3’ or 5’ overhang)
All are palindromes over 2 strands
Restriction Fragment Length Polymorphism (RFLP)
Technique that uses restriction enzyme specificity to distinguish normal from mutant genes. Requires known mutation e.g. w/ mutant, peptide is not cleaved into fragments on southern blot
Proto-oncogene
Normal gene with potential to become oncogene
Oncogene
Gene for a protein that promotes cancer development when deregulated; typically hyperactivates cell properties and has gain of function mutation e.g. MAP kinase signaling cascade
Tumor suppressor gene
Encodes protein that protects from cancer development; usually loss of function in cancer
Chromosomal instability pathway to cancer
As mutations accumulate, genomic stability decreases, resulting in further mutations and increasing chance for double hit
Microsatellite instability pathway
Methylation of tumor suppressor promoters due to upregulation of genes that methylate.
MDM2
Protein that mutually regulates p53; MDM2 downregulates p53 and p53 upregulated MDM2. Under stress, MDM2 dissociates from p53 allowing p53 to exert downstream effects (checkpoint activity). Many cancers upregulate MDM2 accelerating p53 degradation.
CRISPR-Cas9
Cas9 recognizes DNA fragments in CRISPR sequences and uses the guide RNA reference to excise the corresponding DNA from the genome. KO can be done by repairing genome w/ NHEJ or homologous template can be provided for knock-in through homologous recombination.
