MAPRE1 (Microtubule-associated protein, RP/EB family, member 1)

Other names	EB1
HGNC (Hugo)	MAPRE1
LocusID (NCBI)	22919
Location	20q11.21
Location_base_pair	Starts at 31407699 and ends at 31438211 bp from pter ( according to hg19-Feb_2009)  [Mapping]
	EB1-GFP fluorescence on polymerizing microtubule plus ends in a living PtK1 cell.
Note	The original name EB1 came from a yeast two hybrid screen "End Binding 1" is a nickname that was later applied when the protein was found to target to microtubule plus ends.

Description	268 amino acids; 35 kDa; EB1 was cloned in yeast two-hybrid screen as binding partner for the tumor suppressor APC (Adenomatous Polyposis Coli); EB1 is a microtubule plus end tracking protein (+tip). It contains a calponin homology domain and a leucine zipper
Expression	EB1 is ubiquitously expressed. Protein levels remain similar throughout the cell cycle.
Localisation	EB1 targets to the plus ends of microtubules when they are polymerizing, producing a "comet tail" pattern. (Figure 1). The mechanism is treadmilling, in which new subunits are continually added at the tip. EB1 also shows additional weak binding to the microtubule lattice (along the length of the microtubule). EB1 targets to kinetochores moving anti-poleward. This is suspected to be due to binding to kinetochore microtubule plus ends rather than the kinetochore itself. Through its carboxyl terminus, EB1 localizes to centrosomes and spindle poles.
Function	The primary function identified to date is regulation of microtubule dynamic instability. Microtubules dynamically convert between growth (polymerization) and shrinkage (depolymerization). The transition from growth to shrinkage is called catastrophe, while the conversion from shrinkage to growth is called rescue. Microtubules also pause in their polymerization. EB1 reduces these pauses and reduces the frequency of catastrophes. EB1 increases the frequency of rescues. The net result is more stable, longer microtubules. This effect is predominantly seen during mitosis. EB1 is important in maintaining the structure of the mitotic spindle. This is thought to be mediated by its effects on spindle microtubule dynamic instability. EB1 is important in spindle positioning within the cell. This is thought to be due to its effects on astral microtubule dynamic instability. In budding yeast, EB1 also plays a role in positioning the mitotic spindle through the bud neck. In this case, it is through microtubule dynamics as well direct binding to a protein at the bud tip, creating a physical link between the microtubule end and the cell cortex. EB1 plays a role in linking kinetochores to kinetochore microtubules, which is important for chromosome stability. It is not known whether it regulates kinetochore microtubule dynamics or end-on attachment. EB1 also has an independent role in anchoring microtubule minus ends to centrosomes Protein-protein interactions: Adenomatous Polyposis Coli (APC) tumor suppressor, polymerized tubulin (microtubules), p150glued/dynactin, CLIP-170, mDia, Pin2/TRF1, RhoGEF2 (drosophila), shortstop (drosophila)
Homology	MAPRE2, MAPRE3

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