Role of kinetochore in cell division

Cell division is a complex processes.Kinetochore plays a major role.

1. ROLE OF KINETOCHORE IN
CELL DIVISION



Prepared By
Jyoti Shankar Pradhan
MSc Semester II
Roll Number: 17 ZOO 015

Guided By
Prof (Mrs) Pravati Kumari Mahapatra

PG DEPARTMENT OF ZOOLOGY
UTKAL UNIVERSITY, VANI VIHAR

2. INTRODUCTION
To maintain the genetic integrity, eukaryotic cells must segregate their replicated
chromosomes properly during cell division. Chromosome segregation is dependent on
interaction between microtubule and the kinetochore. For proper chromosome segregation,
kinetochore must capture spindle microtubule and connect the sister chromatids of all
chromosomes to opposite poles prior to anaphase onset.
HISTORY
The term Kinetochore was coined in 1934 by L.W. Sharp in his well known text book
Introduction to Cytology. The term “Centromere” was introduced in 1936 by English Biologist
and Geneticist Cyril Dean Darlington. Centromere and Kinetochore were considered synonyms
until 1981. In 1981, Ris and Witt defined the term Kinetochore as the precise region on the
chromosome that gets attached to the spindle fibers.
LOCATION OF THE KINETOCHORE
Kinetochores are the mega-molecular assemblies formed at the centromeric region during late
prophase of human chromosomes. Centromere is the heterochromatic region that consists of
largely repeated sequence known as alpha satellite DNA. The primary candidate for mark of a
kinetochore specification is the presence of CENP- A (a variant of histone H3 in nucleosome).
CENP-A exclusively found at the centromere.
STRUCTURE OF KINETOCHORE
Kinetochore consists of 3 regions: An inner region, outer region and fibrous corona.
KMN PROTEIN NETWORK OF KINETOCHORE
The KMN network is present at the outer kinetochore. It associates with the kinetochore in late
prophase & disappears from the kinetochore in telophase. This network consists of Knl 1
complex ,the Mis 12 complex & the Ndc 80 complex . Function of this network is to link
centromeric DNA to the plus end of microtubule. Inner kinetochore contains a complex of
protein consisting of CENP-C,-H,-I,-K,-L,-M,-N,-O,-P,-S,-T,-U,-V,-W,-X called as the
‘constitutive centromere associated network’ (CCAN). It helps to link the MT- binding KMN
network to the centromeric DNA.
MOLECULAR DISTRIBUTION ALONG THE AXIS OF KINETOCHORE MICROTUBULE

3. FUNCTIONS OF THE KINETOCHORE
1. Association with microtubules .
2. Facilitation of Spindle assembly check point.
3. Depolymerization of microtubules.
TYPES OF KINETOCHORE & MICROTUBULE ATTACHMENT
1. When both sister kinetochores are attached to microtubule from the opposite spindle poles,
then it is amphitelic.
2. A single microtubule from a spindle pole binds to one kinetochore in a sister chromatid pair is
monotelic.
3. Microtubule from same spindle poles can attach to both sister kinetochore called as syntelic.
4. Microtubule from both the spindle pole attach to the same kinetochore is merotelic.



AURORA B REGULATES MICROTUBULE ATTACHMENT AT THE KINETOCHORE

4. Sl. No. phases Activity of Kinetochore
1. Prophase At late prophase kinetochore is
assembled in the centromere.
2. Pro-
metaphase
Sister chromatids are associated with
the spindle fibers.
3. Metaphase Sister chromatids are congressed in
the metaphase plate
4. Anaphase Sister chromatids starts to separate to
opposite poles.

CONGRESSION.
The mechanism by which the chromosomes are brought to spindle equator is known as
congression.
In mitosis, there is separation of sister chromatids occur, but in meiosis I separation of
homologous pair of chromosomes occur.
When the chromosomes properly bind to the microtubule at metaphase then there will be
activation of protein complex APC/ C which promote metaphase to anaphase. In anaphase the
sister chromatids moves to the opposite pole. This APC is responsible for degradation of M-cdk
and mitotic exit occur.
CONCLUSION
Kinetochore plays a vital role in the segregation of chromosomes during cell division. Failure of
this mechanism result in many chromosomal aberrations.