Transcript Lecture 22: Cancer II and Cell Junctions

Cancer II
Six ways of losing the remaining good copy of a
tumor suppressor gene
When proto-oncogene becomes overactive it
becomes an oncogene
Myc Gene Amplification
Mitogens stimulate G1-Cdk and G1/S-Cdk activities
Ocogene collaboration in transgenic mice
Viruses May cause Cancer
Papillomavirus causes warts and subverts the control of cell division
Pap smears
normal
abnormal
invasive
How papillomaviruses are thought to give rise to
cancer of the uterine cervix
Activation of cell proliferation by DNA tumor
virus
Sequence of genetic changes underlying the
development of a colorectal carcinoma
Each tumor will contain a different set of
mutations
Effect of ionizing radiation on normal and cancer cells
Cell Junctions, Cell Adhesion,
and the Extracellular Matrix
Chapter 19
Cross sectional view of intestinal wall
Tracer molecules can not cross tight junctions
Structure of tight junction
Electron Micrograph of tight junctions
Model of tight junction
Claudins are main component of sealing strands
Anchoring junctions in an epithelium
Anchoring junctions are formed by proteins
Cadherins connect actin filaments of different cells
DVD Clip 82
Desmosomes and hemidesmosomes both link to
intermediate filaments
Cadherins also bind intermediate filaments together
Integrins link extracellular matrix to cytoskeleton
Size of gap junction channel can be determined
with fluorescent molecules of different sizes
A Gap junction connexon is made up of 6
transmembrane connexin subunits
Images of gap junctions
The permeability of gap junctions can be regulated
dopamine treatment reduces permeability of gap junctions to a fluorescent dye
Summary of cell junctions found in the cell
Summary of cell junctions found in the cell
In plant cells plasmodesmata perform many of
the same functions as gap junctions
View of plasmodesmata
Structure of Cadherin – responsible for cell to
cell adhesion in vertebrate cells
Ca2+ is required to establish cell to cell
connection through cadherin
Three mechanisms that mediate cell-cell
adhesion
cadherins
least common
Cadherins allow cells to sort themselves
Catenins join cadherins to actin filaments in
adherence junctions
Summary of junctional and non-junctional
adhesive mechanisms