Limits...
Human chromokinesin KIF4A functions in chromosome condensation and segregation.

Mazumdar M, Sundareshan S, Misteli T - J. Cell Biol. (2004)

Bottom Line: Here, we show that human chromokinesin human HKIF4A (HKIF4A) is an essential chromosome-associated molecular motor involved in faithful chromosome segregation.HKIF4A interacts with the condensin I and II complexes and HKIF4A depletion results in chromosome hypercondensation, suggesting that HKIF4A is required for maintaining normal chromosome architecture.Our results provide functional evidence that human KIF4A is a novel component of the chromosome condensation and segregation machinery functioning in multiple steps of mitotic division.

View Article: PubMed Central - PubMed

Affiliation: National Cancer Institute, National Institutes of Health, Bldg. 41, Rm. B 507, 41 Library Dr., Bethesda, MD 20892, USA. mazumdam@mail.nih.gov

ABSTRACT
Accurate chromosome alignment at metaphase and subsequent segregation of condensed chromosomes is a complex process involving elaborate and only partially characterized molecular machinery. Although several spindle associated molecular motors have been shown to be essential for mitotic function, only a few chromosome arm--associated motors have been described. Here, we show that human chromokinesin human HKIF4A (HKIF4A) is an essential chromosome-associated molecular motor involved in faithful chromosome segregation. HKIF4A localizes in the nucleoplasm during interphase and on condensed chromosome arms during mitosis. It accumulates in the mid-zone from late anaphase and localizes to the cytokinetic ring during cytokinesis. RNA interference--mediated depletion of HKIF4A in human cells results in defective prometaphase organization, chromosome mis-alignment at metaphase, spindle defects, and chromosome mis-segregation. HKIF4A interacts with the condensin I and II complexes and HKIF4A depletion results in chromosome hypercondensation, suggesting that HKIF4A is required for maintaining normal chromosome architecture. Our results provide functional evidence that human KIF4A is a novel component of the chromosome condensation and segregation machinery functioning in multiple steps of mitotic division.

Show MeSH

Related in: MedlinePlus

Dynamic localization of HKIF4A during the cell cycle. (A) Schematic representation of the protein domain used for generating an mAb against HKIF4A. Subcellular fractionation of nonsynchronized MRC-5 cells showed that the majority of the endogenous protein is present in the nucleus. Total, total cell extract; Cyto, cytoplasmic extract; Nuc, nuclear extract. Same amounts of protein were loaded in each lane. (B) Non-synchronized MRC-5 cells were fixed and double stained with HKIF4A (red) and DAPI (blue) at different phases of the cell cycle. During interphase the protein was prominently nuclear but from prophase to telophase HKIF4A was present on chromosome arms. In addition, the protein accumulated in the mid-zone (arrow) and formed the cytokinetic ring until cytokinesis. The inset shows an amplified image of the mid-body that appears as two rings. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172419&req=5

fig1: Dynamic localization of HKIF4A during the cell cycle. (A) Schematic representation of the protein domain used for generating an mAb against HKIF4A. Subcellular fractionation of nonsynchronized MRC-5 cells showed that the majority of the endogenous protein is present in the nucleus. Total, total cell extract; Cyto, cytoplasmic extract; Nuc, nuclear extract. Same amounts of protein were loaded in each lane. (B) Non-synchronized MRC-5 cells were fixed and double stained with HKIF4A (red) and DAPI (blue) at different phases of the cell cycle. During interphase the protein was prominently nuclear but from prophase to telophase HKIF4A was present on chromosome arms. In addition, the protein accumulated in the mid-zone (arrow) and formed the cytokinetic ring until cytokinesis. The inset shows an amplified image of the mid-body that appears as two rings. Bar, 5 μm.

Mentions: To gain insight into HKIF4A function, we raised a mouse mAb specific against the extreme COOH-terminal domain of human chromokinesin HKIF4A (Fig. 1 A; see Materials and methods). In Western blots of MRC-5 cell extracts, the HKIF4A antibody detected a single band of 140 kD (Fig. 1 A). In subcellular fractionation of nonsynchronized cells, the protein was highly enriched in the nuclear extract and only trace amounts were detected in the cytoplasmic fraction (Fig. 1 A). During mitosis HKIF4A associates along the entire arms of condensed chromosomes (Fig. 1 B). In addition to the chromosomal localization, the protein accumulates in the mid-zone from anaphase A to cytokinesis (Fig. 1 B). From anaphase B to cytokinesis HKIF4A is present in the mid-body as two distinct rings connecting the MTs from the two half spindles (Fig. 1 B, inset). In late cytokinesis, until the two daughter cells pinch off, the protein persists in the center of the mid-body (Fig. 1 B). Costaining of HKIF4A with tubulin shows partial colocalization at the spindle poles and at the central spindle (Fig. S1, available at http://www.jcb.org/cgi/content/full/jcb.200401142/DC1).


Human chromokinesin KIF4A functions in chromosome condensation and segregation.

Mazumdar M, Sundareshan S, Misteli T - J. Cell Biol. (2004)

Dynamic localization of HKIF4A during the cell cycle. (A) Schematic representation of the protein domain used for generating an mAb against HKIF4A. Subcellular fractionation of nonsynchronized MRC-5 cells showed that the majority of the endogenous protein is present in the nucleus. Total, total cell extract; Cyto, cytoplasmic extract; Nuc, nuclear extract. Same amounts of protein were loaded in each lane. (B) Non-synchronized MRC-5 cells were fixed and double stained with HKIF4A (red) and DAPI (blue) at different phases of the cell cycle. During interphase the protein was prominently nuclear but from prophase to telophase HKIF4A was present on chromosome arms. In addition, the protein accumulated in the mid-zone (arrow) and formed the cytokinetic ring until cytokinesis. The inset shows an amplified image of the mid-body that appears as two rings. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172419&req=5

fig1: Dynamic localization of HKIF4A during the cell cycle. (A) Schematic representation of the protein domain used for generating an mAb against HKIF4A. Subcellular fractionation of nonsynchronized MRC-5 cells showed that the majority of the endogenous protein is present in the nucleus. Total, total cell extract; Cyto, cytoplasmic extract; Nuc, nuclear extract. Same amounts of protein were loaded in each lane. (B) Non-synchronized MRC-5 cells were fixed and double stained with HKIF4A (red) and DAPI (blue) at different phases of the cell cycle. During interphase the protein was prominently nuclear but from prophase to telophase HKIF4A was present on chromosome arms. In addition, the protein accumulated in the mid-zone (arrow) and formed the cytokinetic ring until cytokinesis. The inset shows an amplified image of the mid-body that appears as two rings. Bar, 5 μm.
Mentions: To gain insight into HKIF4A function, we raised a mouse mAb specific against the extreme COOH-terminal domain of human chromokinesin HKIF4A (Fig. 1 A; see Materials and methods). In Western blots of MRC-5 cell extracts, the HKIF4A antibody detected a single band of 140 kD (Fig. 1 A). In subcellular fractionation of nonsynchronized cells, the protein was highly enriched in the nuclear extract and only trace amounts were detected in the cytoplasmic fraction (Fig. 1 A). During mitosis HKIF4A associates along the entire arms of condensed chromosomes (Fig. 1 B). In addition to the chromosomal localization, the protein accumulates in the mid-zone from anaphase A to cytokinesis (Fig. 1 B). From anaphase B to cytokinesis HKIF4A is present in the mid-body as two distinct rings connecting the MTs from the two half spindles (Fig. 1 B, inset). In late cytokinesis, until the two daughter cells pinch off, the protein persists in the center of the mid-body (Fig. 1 B). Costaining of HKIF4A with tubulin shows partial colocalization at the spindle poles and at the central spindle (Fig. S1, available at http://www.jcb.org/cgi/content/full/jcb.200401142/DC1).

Bottom Line: Here, we show that human chromokinesin human HKIF4A (HKIF4A) is an essential chromosome-associated molecular motor involved in faithful chromosome segregation.HKIF4A interacts with the condensin I and II complexes and HKIF4A depletion results in chromosome hypercondensation, suggesting that HKIF4A is required for maintaining normal chromosome architecture.Our results provide functional evidence that human KIF4A is a novel component of the chromosome condensation and segregation machinery functioning in multiple steps of mitotic division.

View Article: PubMed Central - PubMed

Affiliation: National Cancer Institute, National Institutes of Health, Bldg. 41, Rm. B 507, 41 Library Dr., Bethesda, MD 20892, USA. mazumdam@mail.nih.gov

ABSTRACT
Accurate chromosome alignment at metaphase and subsequent segregation of condensed chromosomes is a complex process involving elaborate and only partially characterized molecular machinery. Although several spindle associated molecular motors have been shown to be essential for mitotic function, only a few chromosome arm--associated motors have been described. Here, we show that human chromokinesin human HKIF4A (HKIF4A) is an essential chromosome-associated molecular motor involved in faithful chromosome segregation. HKIF4A localizes in the nucleoplasm during interphase and on condensed chromosome arms during mitosis. It accumulates in the mid-zone from late anaphase and localizes to the cytokinetic ring during cytokinesis. RNA interference--mediated depletion of HKIF4A in human cells results in defective prometaphase organization, chromosome mis-alignment at metaphase, spindle defects, and chromosome mis-segregation. HKIF4A interacts with the condensin I and II complexes and HKIF4A depletion results in chromosome hypercondensation, suggesting that HKIF4A is required for maintaining normal chromosome architecture. Our results provide functional evidence that human KIF4A is a novel component of the chromosome condensation and segregation machinery functioning in multiple steps of mitotic division.

Show MeSH
Related in: MedlinePlus