Biomedical subjects

Henderika M J Hut

Publications and source records attributed to Henderika M J Hut.

3 recordsLinked to original sources

PubMed2005

Dysfunctional BRCA1 is only indirectly linked to multiple centrosomes.

A remarkable and yet unexplained phenomenon in cancer cells is the presence of multiple centrosomes, organelles required for normal cell division. Previously, it was demonstrated that the tumor suppressor BRCA1 is a component of centrosomes. This observation led to the hypothesis that defective BRCA1 results in malfunctioning centrosomes and faulty centrosomes are a possible cause of cancer. Using EGFP-tagged fusion proteins and BRCA1(-/-) cells we show that although some BRCA1 antibodies do label centrosomes under certain fixation conditions, BRCA1 is not a centrosomal protein. Therefore, it is unlikely that a mutation in BRCA1 directly alters centrosome structure and function. BRCA1 plays an established role in DNA damage repair and in G2/M checkpoint regulation. We present evidence that multiple centrosomes can arise in any cell when G2/M checkpoint fails and entrance into mitosis occurs in the presence of DNA damage.

Antibodies↗

PubMed2005

Hsp70 protects mitotic cells against heat-induced centrosome damage and division abnormalities.

The effect of heat shock on centrosomes has been mainly studied in interphase cells. Centrosomes play a key role in proper segregation of DNA during mitosis. However, the direct effect and consequences of heat shock on mitotic cells and a possible cellular defense system against proteotoxic stress during mitosis have not been described in detail. Here, we show that mild heat shock, applied during mitosis, causes loss of dynamitin/p50 antibody staining from centrosomes and kinetochores. In addition, it induces division errors in most cells and in the remaining cells progression through mitosis is delayed. Expression of heat shock protein (Hsp)70 protects against most heat-induced division abnormalities. On heat shock, Hsp70 is rapidly recruited to mitotic centrosomes and normal progression through mitosis is observed immediately after release of Hsp70 from centrosomes. In addition, Hsp70 expression coincides with restoration of dynamitin/p50 antibody staining at centrosomes but not at kinetochores. Our data show that during mitosis, centrosomes are particularly affected resulting in abnormal mitosis. Hsp70 is sufficient to protect against most division abnormalities, demonstrating the involvement of Hsp70 in a repair mechanism of heat-damaged mitotic centrosomes.

Animals↗

PubMed2003

Centrosomes split in the presence of impaired DNA integrity during mitosis.

A well-established function of centrosomes is their role in accomplishing a successful mitosis that gives rise to a pair of identical daughter cells. We recently showed that DNA replication defects and DNA damage in Drosophila embryos trigger centrosomal changes, but it remained unclear whether comparable centrosomal responses can be provoked in somatic mammalian cells. To investigate the centrosomal organization in the presence of impaired DNA integrity, live and ultrastructural analysis was performed on gamma-tubulin-GFP and EGFP-alpha-tubulin-expressing Chinese hamster ovary cells. We have shown that during mitosis in the presence of incompletely replicated or damaged DNA, centrosomes split into fractions containing only one centriole. This results in the formation of multipolar spindles with extra centrosome-like structures. Despite the extra centrosomes and the multipolarity of the spindles, cells do exit from mitosis, resulting in severe division errors. Our data provide evidence of a novel mechanism showing how numerous centrosomes and spindle defects can arise and how this can lead to the formation of aneuploid cells.

Actins↗