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The microtubule-dependent motor centromere-associated protein E (CENP-E) is an integral component of kinetochore corona fibers that link centromeres to spindle microtubules.

Yao X, Anderson KL, Cleveland DW - J. Cell Biol. (1997)

Bottom Line: Centromere-associated protein E (CENP-E) is a kinesin-related microtubule motor protein that is essential for chromosome congression during mitosis.In congressing chromosomes, CENP-E is preferentially associated with (or accessible at) the stretched, leading kinetochore known to provide the primary power for chromosome movement.Taken together, this evidence strongly supports a model in which CENP-E functions in congression to tether kinetochores to the disassembling microtubule plus ends.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Cell Biology, Ludwig Institute for Cancer Research, School of Medicine, University of California, La Jolla, CA 92093-0660, USA.

ABSTRACT
Centromere-associated protein E (CENP-E) is a kinesin-related microtubule motor protein that is essential for chromosome congression during mitosis. Using immunoelectron microscopy, CENP-E is shown to be an integral component of the kinetochore corona fibers that tether centromeres to the spindle. Immediately upon nuclear envelope fragmentation, an associated plus end motor trafficks cytoplasmic CENP-E toward chromosomes along astral microtubules that enter the nuclear volume. Before or concurrently with initial lateral attachment of spindle microtubules, CENP-E targets to the outermost region of the developing kinetochores. After stable attachment, throughout chromosome congression, at metaphase, and throughout anaphase A, CENP-E is a constituent of the corona fibers, extending at least 50 nm away from the kinetochore outer plate and intertwining with spindle microtubules. In congressing chromosomes, CENP-E is preferentially associated with (or accessible at) the stretched, leading kinetochore known to provide the primary power for chromosome movement. Taken together, this evidence strongly supports a model in which CENP-E functions in congression to tether kinetochores to the disassembling microtubule plus ends.

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An associated plus  end motor activity trafficks  CENP-E along newly assembled astral microtubules into  the nuclear domain after nuclear envelope fragmentation. HeLa cells were processed as described in  Materials and Methods. (A)  Low magnification view of a  prophase/prometaphase HeLa  cell bearing condensed chromosomes and a partially  fragmented nuclear envelope. One spindle pole is  readily apparent (asterisk).  Examination of serial sections did not reveal another  pole, consistent with a prophase cell before centriole  separation. (B) Magnified  view of boxed region in A  shows that astral microtubules emanating from the  centriole come in close proximity to the nuclear envelope.  (C) Higher magnification  view reveals that CENP-E is  microtubule-associated along  astral microtubules adjacent  to the remaining nuclear envelope (bracket). Arrowheads  point to microtubule-bound  gold particles reporting  CENP-E location. (D) Magnified view of the dashed box  in A and highlighting astral  microtubules passing through  the fragmented lamina and  lying in close proximity to  a chromosome. (E) Higher  magnification of the area  boxed in D, revealing that  some CENP-E is found along  the microtubules, but additional CENP-E is associated  with a localized domain on the chromosome, presumably the developing kinetochore. Note the chromosome is not yet attached to microtubules. Bars: (A) 2 μm; (B) 400 nm; (C) 200 nm; (D) 800 nm; (E) 140 nm.
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Figure 2: An associated plus end motor activity trafficks CENP-E along newly assembled astral microtubules into the nuclear domain after nuclear envelope fragmentation. HeLa cells were processed as described in Materials and Methods. (A) Low magnification view of a prophase/prometaphase HeLa cell bearing condensed chromosomes and a partially fragmented nuclear envelope. One spindle pole is readily apparent (asterisk). Examination of serial sections did not reveal another pole, consistent with a prophase cell before centriole separation. (B) Magnified view of boxed region in A shows that astral microtubules emanating from the centriole come in close proximity to the nuclear envelope. (C) Higher magnification view reveals that CENP-E is microtubule-associated along astral microtubules adjacent to the remaining nuclear envelope (bracket). Arrowheads point to microtubule-bound gold particles reporting CENP-E location. (D) Magnified view of the dashed box in A and highlighting astral microtubules passing through the fragmented lamina and lying in close proximity to a chromosome. (E) Higher magnification of the area boxed in D, revealing that some CENP-E is found along the microtubules, but additional CENP-E is associated with a localized domain on the chromosome, presumably the developing kinetochore. Note the chromosome is not yet attached to microtubules. Bars: (A) 2 μm; (B) 400 nm; (C) 200 nm; (D) 800 nm; (E) 140 nm.

Mentions: To examine CENP-E localization as it first associates with chromosomes and/or spindle microtubules, we carried out immunoelectron microscopy on a cell in late prophase/earliest prometaphase, just as the nuclear envelope had started to disassemble (Fig. 2 A). At this point, astral microtubules emanate from centrioles, reach the remaining nuclear envelope (Fig. 2 C, bracket), and in some instances pass though gaps in the envelope, coming in close proximity to newly condensing chromosomes (Fig. 2, D and E). Even at these earliest times, gold particles representing the labeling of CENP-E are found almost exclusively along astral microtubules or at developing kinetochores adjacent to microtubules that have penetrated into the nuclear volume. CENP-E bound to astral microtubules was often closely associated with electron-dense structures (Fig. 2 C, upper left, arrowhead). No similar structures were found in cells before onset of mitosis, suggesting the assembly of a CENP-E–containing complex just at the onset of mitosis. Some CENP-E was found localized to domains of the condensing chromatin (Fig. 2, D and E, arrowhead). Careful examination of serial sections of chromosomes did not reveal any trilaminar kinetochore structures, nor were any microtubules obviously attached laterally or end on. However, in light of CENP-E's association with more mature kinetochores (see below), we infer that these areas of chromosome-bound CENP-E represent the immature kinetochores. All chromosomes with more than one gold particle representing bound CENP-E did have astral microtubules within 200 ± 40 nm (e.g., Fig. 2, D and E, arrowhead). Virtually no gold particles were found on other structures (i.e., vesicular membranes or at other surface regions of the chromosomes) (Fig. 2 D).


The microtubule-dependent motor centromere-associated protein E (CENP-E) is an integral component of kinetochore corona fibers that link centromeres to spindle microtubules.

Yao X, Anderson KL, Cleveland DW - J. Cell Biol. (1997)

An associated plus  end motor activity trafficks  CENP-E along newly assembled astral microtubules into  the nuclear domain after nuclear envelope fragmentation. HeLa cells were processed as described in  Materials and Methods. (A)  Low magnification view of a  prophase/prometaphase HeLa  cell bearing condensed chromosomes and a partially  fragmented nuclear envelope. One spindle pole is  readily apparent (asterisk).  Examination of serial sections did not reveal another  pole, consistent with a prophase cell before centriole  separation. (B) Magnified  view of boxed region in A  shows that astral microtubules emanating from the  centriole come in close proximity to the nuclear envelope.  (C) Higher magnification  view reveals that CENP-E is  microtubule-associated along  astral microtubules adjacent  to the remaining nuclear envelope (bracket). Arrowheads  point to microtubule-bound  gold particles reporting  CENP-E location. (D) Magnified view of the dashed box  in A and highlighting astral  microtubules passing through  the fragmented lamina and  lying in close proximity to  a chromosome. (E) Higher  magnification of the area  boxed in D, revealing that  some CENP-E is found along  the microtubules, but additional CENP-E is associated  with a localized domain on the chromosome, presumably the developing kinetochore. Note the chromosome is not yet attached to microtubules. Bars: (A) 2 μm; (B) 400 nm; (C) 200 nm; (D) 800 nm; (E) 140 nm.
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Figure 2: An associated plus end motor activity trafficks CENP-E along newly assembled astral microtubules into the nuclear domain after nuclear envelope fragmentation. HeLa cells were processed as described in Materials and Methods. (A) Low magnification view of a prophase/prometaphase HeLa cell bearing condensed chromosomes and a partially fragmented nuclear envelope. One spindle pole is readily apparent (asterisk). Examination of serial sections did not reveal another pole, consistent with a prophase cell before centriole separation. (B) Magnified view of boxed region in A shows that astral microtubules emanating from the centriole come in close proximity to the nuclear envelope. (C) Higher magnification view reveals that CENP-E is microtubule-associated along astral microtubules adjacent to the remaining nuclear envelope (bracket). Arrowheads point to microtubule-bound gold particles reporting CENP-E location. (D) Magnified view of the dashed box in A and highlighting astral microtubules passing through the fragmented lamina and lying in close proximity to a chromosome. (E) Higher magnification of the area boxed in D, revealing that some CENP-E is found along the microtubules, but additional CENP-E is associated with a localized domain on the chromosome, presumably the developing kinetochore. Note the chromosome is not yet attached to microtubules. Bars: (A) 2 μm; (B) 400 nm; (C) 200 nm; (D) 800 nm; (E) 140 nm.
Mentions: To examine CENP-E localization as it first associates with chromosomes and/or spindle microtubules, we carried out immunoelectron microscopy on a cell in late prophase/earliest prometaphase, just as the nuclear envelope had started to disassemble (Fig. 2 A). At this point, astral microtubules emanate from centrioles, reach the remaining nuclear envelope (Fig. 2 C, bracket), and in some instances pass though gaps in the envelope, coming in close proximity to newly condensing chromosomes (Fig. 2, D and E). Even at these earliest times, gold particles representing the labeling of CENP-E are found almost exclusively along astral microtubules or at developing kinetochores adjacent to microtubules that have penetrated into the nuclear volume. CENP-E bound to astral microtubules was often closely associated with electron-dense structures (Fig. 2 C, upper left, arrowhead). No similar structures were found in cells before onset of mitosis, suggesting the assembly of a CENP-E–containing complex just at the onset of mitosis. Some CENP-E was found localized to domains of the condensing chromatin (Fig. 2, D and E, arrowhead). Careful examination of serial sections of chromosomes did not reveal any trilaminar kinetochore structures, nor were any microtubules obviously attached laterally or end on. However, in light of CENP-E's association with more mature kinetochores (see below), we infer that these areas of chromosome-bound CENP-E represent the immature kinetochores. All chromosomes with more than one gold particle representing bound CENP-E did have astral microtubules within 200 ± 40 nm (e.g., Fig. 2, D and E, arrowhead). Virtually no gold particles were found on other structures (i.e., vesicular membranes or at other surface regions of the chromosomes) (Fig. 2 D).

Bottom Line: Centromere-associated protein E (CENP-E) is a kinesin-related microtubule motor protein that is essential for chromosome congression during mitosis.In congressing chromosomes, CENP-E is preferentially associated with (or accessible at) the stretched, leading kinetochore known to provide the primary power for chromosome movement.Taken together, this evidence strongly supports a model in which CENP-E functions in congression to tether kinetochores to the disassembling microtubule plus ends.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Cell Biology, Ludwig Institute for Cancer Research, School of Medicine, University of California, La Jolla, CA 92093-0660, USA.

ABSTRACT
Centromere-associated protein E (CENP-E) is a kinesin-related microtubule motor protein that is essential for chromosome congression during mitosis. Using immunoelectron microscopy, CENP-E is shown to be an integral component of the kinetochore corona fibers that tether centromeres to the spindle. Immediately upon nuclear envelope fragmentation, an associated plus end motor trafficks cytoplasmic CENP-E toward chromosomes along astral microtubules that enter the nuclear volume. Before or concurrently with initial lateral attachment of spindle microtubules, CENP-E targets to the outermost region of the developing kinetochores. After stable attachment, throughout chromosome congression, at metaphase, and throughout anaphase A, CENP-E is a constituent of the corona fibers, extending at least 50 nm away from the kinetochore outer plate and intertwining with spindle microtubules. In congressing chromosomes, CENP-E is preferentially associated with (or accessible at) the stretched, leading kinetochore known to provide the primary power for chromosome movement. Taken together, this evidence strongly supports a model in which CENP-E functions in congression to tether kinetochores to the disassembling microtubule plus ends.

Show MeSH
Related in: MedlinePlus