Cell Cycle, Apoptosis, and Cancer Flashcards
When is the restriction point (R), and what happens there?
2 hours prior to S phase (in G1)
if growth factors are limiting –> restriction occurs
What two proteins in HPV cause cancer?
E6 and E7
What happens in the G0 phase?
poor nutrient/environmental conditions –> cell withdraws from cell cycle
What do proto-oncogenes normally code for?
growth factors
receptors for GFs and hormones
Transcription factors
(basically anything promoting cell growth and division)
What is p53
transcription factor that is activated when DNA is damaged –> activates p21 –> keeps Rb hypophosphorylated and sequesters E2F so you can’t move into S phase
Promotes apoptosis = tumor suppressor
What does CDC25 phosphatase do?
Undoes WEE1 phosphorylation of C-CDK complex to reactivate it
When do topoisomerase I inhibitors work?
S, G2, and M phases
What does E6 in HPV inhibit?
p53
What are the checkpoints?
R, G1, G2, Metaphase
What is APC/C?
anaphase promoting complex/ cyclosome
a ubiquitin ligase enzyme that adds polyubiquitin to cdk-cyclin complex –> cyclin degrades –> signals change to anaphase
What type of protein is APC?
Mutations in it are linked to what type of cancer?
adenomatous polyposis coli = tumor suppressor
colon cancer
What does the SH2 domain on GRB-2 do?
binds to phosphorylated tyrosine residues on an RTK
What are 2 common toxins that cause p53 mutations?
activated benzopyrene in cigarette smoke and aflatoxin, a fungal metabolite in moldy grain and peanuts
What happens in the G2 phase?
DNA stability is checked
How do alkylating agents work to treat cancer?
block DNA replication
affect all phases of cell cycle
How to antimetabolites work to treat cancer?
inhibit enzymes involved in DNA synthesis
S phase
What is Erbitux?
treats colorectal cancer
mAb directed against EGF receptor that is over-expressed in colorectal cancer
What triggers metaphase to anaphase?
cyclin turnover
APC/C degrades cyclin to help do this
What is the order of the cell cycle?
G0 G1 –> S –> G2 –> M
What happens in the M phase
Mitosis
Chromosome separation
Cell division
What happens in the G1 checkpoint?
occurs in response to DNA damage
timing similar to R (2 hours before S)
What happens in hereditary retinoblastoma?
mutation/deletion of once copy of RB1 is inherited –>
cells are predisposed to be cancerous –> some mutation occurs to eliminate last good copy –> cancer
How can viruses cause cancer?
During virus replication, accidentally incorporates a human proto-oncogene into its genome –> mutation turns it into an oncogene –> virus can now transform normal cells and cause cancer
Which enzyme is missing in many somatic cells that causes their senescence?
telomerase - maintains telomere length
w/out it, telomeres shrink and cells will eventually die
