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26.10.17 Cyclin B1's essential role in mitosis and the timing of entry into mitosis

last modified Nov 14, 2017 09:19 PM
Bernhard Strauss of the former Pines lab and collegues show in this J Cell Biol paper that Cyclin B1 is required for cell division in mouse embryos
26.10.17 Cyclin B1's essential role in mitosis and the timing of entry into mitosis

Fig.3 (excerpt): Early embryos in which some cells lack Cyclin B1 and are not dividing (on the left).

Cyclin B1 is essential for mitosis in mouse embryos, and its nuclear export sets the time for mitosis

Strauss B et al.  (2017) J Cell Biol. Oct 26. pii: jcb.201612147. DOI:10.1083/jcb.201612147 [Epub ahead of print]



There is remarkable redundancy between the Cyclin–Cdk complexes that comprise the cell cycle machinery. None of the mammalian A-, D-, or E-type cyclins are required in development until implantation, and only Cdk1 is essential for early cell divisions. Cyclin B1 is essential for development, but whether it is required for cell division is contentious.

Here, we used a novel imaging approach to analyze Cyclin B1–null embryos from fertilization onward. We show that Cyclin B1−/− embryos arrest in G2 phase after just two divisions. This is the earliest arrest of any Cyclin known and places Cyclin B1 with cdk1 as the essential regulators of the cell cycle. We reintroduced mutant proteins into this genetically null background to determine why Cyclin B1 is constantly exported from the nucleus.

We found that Cyclin B1 must be exported from the nucleus for the cell to prevent premature entry to mitosis, and retaining Cyclin B1–Cdk1 at the plasma membrane precludes entry to mitosis.



The Pines lab has now left the Gurdon Institute; Prof Jonathon Pines is Head of the Division of Cancer Biology at the Institute of Cancer Research in London.

Studying development to understand disease

The Gurdon Institute is funded by Wellcome and Cancer Research UK to study the biology of development, and how normal growth and maintenance go wrong in cancer and other diseases.

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