Dan Foltz
Assistant Professor of Biochemistry & Molecular Genetics
Ph.D., Northwestern University
Assembly and Function of Centromeric Chromatin

Laboratory
Home Page

 

The faithful segregation of chromosomes through each round of cell division is imperative to guard the human genome against errors in chromosome number that can lead to birth defects, cell death or cancer. Integral to this mitotic process is a specialized chromatin domain known as the centromere, which is present on the chromosome throughout the cell cycle. The centromere directs the assembly of the transient macromolecular kinetochore structure during mitosis, which in turn mediates the interaction between the chromosome and spindle microtubules and regulates the progression of cells through mitosis in response to unaligned chromosomes. Centromeric chromatin is assembled around a unique centromeric nucleosome containing Centromere protein-A (CENP-A), in place of histone H3 within the canonical histone octamer (which includes histones H4, H2A and H2B). We are interested in the mechanism by which the CENP-A containing nucleosome directs the assembly of the centromere and contributes to mitotic progression. Using a proteomics approach, we have identified the CENP-A nucleosome-associated complex (CENP-ANAC, an assemblage of six centromere proteins [CENPs]) as the most proximal component of the human centromere. We are interested in determining how this complex distinguishes CENP-A nucleosomes from general histone-H3-containing chromatin and ultimately how this structure is assembled to ensure proper chromosome segregation, as well as beginning to understand the role this macromolecular complex may play during interphase.

We are also interested in the mechanism by which a region of the chromosome is specified as a centromere and how assembly of this chromatin domain is accomplished. The location of the mammalian centromere on each chromosome is stably inherited through each cell cycle. In most eukaryotes (with the exception of S. cerevisiae) the location of the centromere is not dictated by the underlying DNA sequence, and therefore the mechanism of centromere identification is thought to be epigenetic, literally meaning "on top of" the genetic code. Due to the epigenetic nature of the centromere, each round of DNA synthesis presents a challenge for it's stable propagation, since replication of the chromosome requires that new CENP-A nucleosomes are assembled in the proper location in order to maintain the epigenetic mark through successive rounds of cell division. Epigenetic inheritance is often dependent on covalent histone modifications as well as the incorporation of histone variants into chromatin. In the case of the centromere, the CENP-A histone variant plays a central role; however, histone modifications may also be involved. We seek to understand how centromeric chromatin is assembled and how this process is restricted to sites already determined to be active centromeres. While the protein complexes involved in bringing pre-nucleosomal forms of canonical histone H3 to the DNA, as well as the factors required for their assembly into chromatin, are well known, the analogous proteins have not been identified for CENP-A nucleosome assembly. We are using tandem-affinity-tagging in human cell culture coupled with mass spectrometry to identify the proteins and histone modifications involved in centromere assembly. In addition, we use in vitro assays as well as siRNA in mammalian cell culture to determine how these complexes function to assemble the human centromere.


Selected References

Bassett EA, Wood S, Salimian KJ, Ajith S, Foltz DR, Black BE. (2010) "Epigenetic centromere specification directs aurora B accumulation but is insufficient to efficiently correct mitotic errors." J Cell Biol. Jul 190:177-85. Epub 2010 Jul 19. [PubMed]

Stukenberg PT, Foltz DR. (2010) "Kinetochores: orchestrating the chromosomal minuet." Curr Biol. Jun 20(12):R522-5. [PubMed]

Foltz DR, Jansen LE, Bailey AO, Yates JR 3rd, Bassett EA, Wood S, Black BE,Cleveland DW. (2009) "Centromere-specific assembly of CENP-a nucleosomes is mediated by HJURP." Cell. May 137:472-84. [PubMed]

Jansen LE, Black BE, Foltz DR, Cleveland DW. (2007) "Propagation of centromeric chromatin requires exit from mitosis." J Cell Biol. Mar 176:795-805. Epub 2007 Mar 5. [PubMed]

Black BE, Jansen LE, Maddox PS, Foltz DR, Desai AB, Shah JV, Cleveland DW. (2007) "Centromere identity maintained by nucleosomes assembled with histone H3 containing the CENP-A targeting domain." Mol Cell. Jan 25:309-22. [PubMed]

Foltz DR, Jansen LE, Black BE, Bailey AO, Yates JR 3rd, Cleveland DW. (2006) "The human CENP-A centromeric nucleosome-associated complex." Nat Cell Biol. 8:458-69. Epub 2006 Apr 16. [PubMed]

Black BE, Foltz DR, Chakravarthy S, Luger K, Woods VL Jr, Cleveland DW. (2004) "Structural determinants for generating centromeric chromatin." Nature. Jul 430(6999):578-82. [PubMed]

Kops GJ, Foltz DR, Cleveland DW. (2004) "Lethality to human cancer cells through massive chromosome loss by inhibition of the mitotic checkpoint." Proc Natl Acad Sci U S A. Jun 101(23):8699-704. Epub 2004 May 24. [PubMed]

Foltz DR, Jansen LE, Bailey AO, Yates JR 3rd, Bassett EA, Wood S, Black BE,Cleveland DW. (2009) "Centromere-specific assembly of CENP-a nucleosomes is mediated by HJURP." Cell. May 137:472-84. [PubMed]