KNL2 binds to the CENP-A nucleosome throughout interphase and it adds to new CENP-A deposition into centromeres via HJURP and the Mis18 complex. Credit: Original content by Tatsuo Fukagawa
It is coiled around a core made of proteins called histones to form a structure known as a nucleosome when DNA is condensed into chromosomes. The nucleosomes in the centromeric area contain a variant histone protein called CENP-A, which defines the location of the centromere. The systems by which CENP-A is deposited at the centromeres to properly define their location were unidentified until now.
The research study group revealed that during mitosis (the procedure of cellular division), a protein called CENP-C binds CENP-A and functions as a scaffold for other kinetochore proteins. During interphase (the time when the cell is not dividing), a different protein called KNL2 binds to centromeres instead. “KNL2 consists of a CENP-C-like motif and belongs of the Mis18 complex, a licensing element for brand-new CENP-A deposition,” describes lead authors of the research study Honghui Jiang and Mariko Ariyoshi.
CENP-C omits KNL2 from the CENP-A-KNL2 complex during mitosis. Credit: Original material by Tatsuo Fukagawa
The group even more exposed that this interaction in between KNL2 and the centromere is needed for new deposition of CENP-A during interphase, which in turn assists preserve the correct place of the centromere. “We likewise revealed that CENP-C is phosphorylated throughout mitosis, and phosphorylated CENP-C excludes KNL2 from the KNL2– CENP-A complex,” describes senior author Tatsuo Fukagawa.
These brand-new insights into the structure of the centromeric area will prove vital beforehand knowledge of cellular division and development. Proteins associated with cellular division and the kinetochore are targets for anti-cancer drugs; therefore, this work will also add to the design of novel drugs for illness such as cancer.
Reference: “The cryo-EM structure of the CENP-A nucleosome in complex with ggKNL2” 6 February 2023, EMBO Journal.DOI: 10.15252/ embj.2022111965.
Funding: Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology, Japan Science and Technology Agency.
The research study team revealed that during mitosis (the procedure of cell department), a protein called CENP-C binds CENP-A and acts as a scaffold for other kinetochore proteins. “KNL2 includes a CENP-C-like theme and is a part of the Mis18 complex, a licensing element for brand-new CENP-A deposition,” describes lead authors of the research study Honghui Jiang and Mariko Ariyoshi.
The group even more revealed that this interaction in between KNL2 and the centromere is needed for new deposition of CENP-A throughout interphase, which in turn assists preserve the correct location of the centromere. “We likewise showed that CENP-C is phosphorylated throughout mitosis, and phosphorylated CENP-C excludes KNL2 from the KNL2– CENP-A complex,” discusses senior author Tatsuo Fukagawa. CENP-C preferentially binds to CENP-A, enabling the formation of the kinetochore for cell department.
Cryo EM structure of the CENP-A nucleosome complex with KNL2. Credit: Jiang et al., EMBO J., 2023
Researchers led by Osaka University have utilized cryogenic electron microscopy analysis to expose the structural change of the centromere at an atomic level during cell department.
The genetic product inside cells is arranged into structures called chromosomes. The centromere is important for the proper division of the chromosomes by means of interaction with spindle microtubules when cells divide and grow. Now, a research study by researchers at Osaka University has clarified the structure of the centromeric region in chicken cells utilizing a method called cryogenic electron microscopy (cryo-EM).
Cryo-EM freezes samples rapidly to protect and stabilize them, and then images them utilizing accidents with electrons to reveal their structure. A complex of proteins called the “kinetochore” forms at the centromeric area, and this is essential for cells to divide properly. The researchers had the ability to clarify a structural change to the kinetochore at the atomic level using cryo-EM analysis.
