CONTENTS |
HISTOLOGY FOR MEDICAL STUDENTS
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ATLAS OF HISTOLOGY IMAGES |
CELL CYCLE REGULATION
Cdk2 (p33) - cyclin-dependent kinase is regulated by phosphorylation in similar fashion as cdc2; can associate with A, E, D1, D3 cyclins; complex Cdk2+A-cyclin is present in S and G2 periods, it is associated with DNA in the initiation complex during replication; but complex cdc2+A-cyclin is present only in G2; copmlex Cdk2+E-cyclin is active in the G1 and S-phases and is important for the progression from G1 to S
Cdk3 - regulated by p35
Cdk4 - cyclin-dependent kinase which associates
with cyclins D1, D2, D3; activity of this kinase is regulated by
phosphorylation of specific treonine residues; active cdk4+D1-cyclin complex
can phosphorylate of retinoblastoma gene product (pRb)
Cdk5 - (p35) is localised in brain, in other
tissues it is expressed in a truncated form, designated p25
Cdk6 - involved in G1 to S progression, complex
Cdk4+D-cyclins can regulate phosphorylation pRb
Cdk7 - binds H-cyclin; this complex is required for
phosphorylation of the complex Cdc2+B-cyclin, that is necessary for G2/M
transistion; can also phosphorylate Cdk2, Cdk4 on specific regulatort treonine
sites; can functioning as a TFIH subunit by phosphorylation the C-terminal
domain of the lagerst subunit of RNA polymerase
Cdc16 - it is localised in the mitotic spindle
centrosome; maybe it is required for cyclin degradation
Cdc34 - is required for the late G1-S transistion; this is ubiquitin-conjugating ligand; takes part in ubiquitination of G1 cyclins
p14 -
p15 - a member of p16 family, strondly upregulated
by TGF-beta
p16 - inhibitor of Cdk4+D-cyclins interferes
followed by preventation phosphorylation of pRb by Cdk4+D-cyclins
p18 -
p19 -
p21 (Cip1) - inhibitor of cdk activity in a
quaternary complex that also included cyclin D, Cdk4, PCNA; p21 can bind and
inhibit each member of cdk family; p21 can directly bind to PCNA and inhibit
DNA replication
p27 (Kip1) - inhibitor of cdk; can bind to
Cdk4+D-cyclin (preferentially), Cdk2+E-cyclin, Cdk2+A-cyclin and inhibit their
cdk activity; in normal cells p27 is
gradually reduced when cells reach S-period, but TGF-beta can prevent this
followed the cell arrest in G1-phase; important for G1-S transistion
p35 - is Cdk5
p53 - can activate p21
p107 - contains region which is similar to that in
pRb, pRb2 and which can associate with E2F transcription factor
pRb - (p110) retinoblastoma gene product nuclear
phosphoprotein which undregoes differential phosphorylation during the cell
cycle; a number of cellular proteins interact with hypophosphorylated pRb
including: E2F transcription factor, several cyclins, RBP-1, RBP-2, c-myc,
N-myc, p46; during G1-phase pRb is predominantly hypophosphorylated state and
it becomes increasingly phosphorylated through the cell cycle until late of
mitosis when substantial dephosphorylation occurs
pRb2 - protein 120 kDa which shows a high degree of
identifywith pRb and related p107 protein; contains region binding E2F
transcription factor
MDM2
- can function to bind p53 and thereby block
p53-mediated transactivation of cotransfected reporter constructs, to limit the
length p53-mediated growth arrest following DNA damage
FAS (APO 1; CD-95) -
FAS ligands (FAS-L) and tumor
necrosis factors (TNFs) function as rapid inducers of cell deth; both of these
ligands mediate their effects throughstructurally related receptors belonging
th the TNF-R superfamily of type II receptors; FAS and TNF-R1 (receptor) share
a unique cytoplasmic motif coined the “deth domain”, three additional proteins TRADD, FADD, RIP also contain “deth
domain”
TRAIL (APO-2) - TNF-related apoptosos inducing ligand
belongs TNF family member, rapidly induces apoptosis
FAF1 -
FAS-associated factor specifically interacts
with cytoplasmic domain FAS and potentiates FAS-induced apoptosis
CAS (p100)
- cellular
apoptosis susceptibility; plays an important role in both toxin and TNF
mediated cell death, as well as in cell proliferation; CAS expression increases
when resting cells are induced to proliferate and decrease when they are growth
arrested
Bcl-2
- blocks cell death following a variety of
stimuli
Bax
(p21) - form a complex with Bcl-2; overexpression of
ob Bax accelerates apoptotic cell death
Bcl-xL - belongs to Bcl/Bax family;
represses cell death, while its short form Bcl-xS favors cell death
Bad
-
belongs to Bcl/Bax family; selectively dimerizes with Bcl-xL , as well as with Bcl-2; Bad binds more strongly to
Bcl-xL than to Bcl-2 and reverses the death
repressor activity of Bcl-xL
but not of Bcl-2
Bcl-w - belongs to Bcl/Bax
family;
A1 related protein (Bfl-1) -
belongs to Bcl/Bax family;
Bag-1 -
belongs to Bcl/Bax family; Bcl-2 binding
protein; anti-death;
CYCLINS
PCNA - proliferating cell nuclear antigen; ia
auxillary protein of DNA polymerase sigma; is synthesized in early G1 and
S-phases
cyclin D1 - (product of PRAD1 or BCL1 gene) is
synthesized in late G1 and appears to be required for progression into S-phase;
overexpression of D1-cyclin leads to the reduction of length of G1
cyclin D3 - can associate with Cdk5 and weakly with
Cdk2; function is not so clear; in T-cells, where D1-cyclin is absent,
D3-cyclin binds Cdk4; while the D-type cyclins are associated with cdk, these
can bind PCNA
cyclin A - is required for S-pase and passage through
G2; disruption of normal cyclin A expression will cause cells to arrest at G2;
binds Cdk2 near the start of S-phase; may be necessary for the initiation of
DNA prelication
cyclin C - maybe, it can activate Cdc2 or a related Cdk
at the G1 restriction point
cyclin E
- activates Cdk2 near the start of S-phase, to
be necessary for the initiation of DNA replication - S-phase
cyclin B - is a critical regulator of mitosis;
associate with inactive Cdc2; inactive complex Cdc2+B-cyclin is accumulated
until the end of G2, then Cdc2 is phosphrylated by p25 at thr-14 and thr15 and
the complex appears to be active and the cell grive into M-phase; this complex
remains active until methaphase/anaphase when cyclin B becomes degraded; this
degradation process appears to be
ubiqutin-dependent and is necessary for the cell exit mitosis
cyclin H - binds Cdk7, complex Cdk7+H-cyclin
phosphorylates Cdc2 in complex with B-cyclin followed passing the cell from G2
to M-phase
KAP - is a protein phosphatase, can bind Cdk2 and
Cdc2 and regulate phosphorylation of these
JAK1 - is required for the phosphorilation og the
transcription factor Stat1 (p91) in responce to INF-alpha or gamma, and for
phosphorilation of Stat2(p113) in response to INF-alpha
GADD Genes - p53
can upregulate expression GADD45, which inhibits entry of cells into S-phase
and apparently acts in concert with GADD153 in inducing growth arrest;
expression of GADD153 is increased after DNA damage and independent of p53
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