The nuclear scaffold protein SAF-A is required for kinetochore-microtubule attachment and contributes to the targeting of Aurora-A to mitotic spindles.
Segregation of chromosomes during cell division requires correct formation of mitotic spindles. Here, we show that a scaffold attachment factor A (SAF-A), also known as heterogeneous nuclear ribonucleoprotein-U, contributes to the attachment of spindle microtubules (MTs) to kinetochores and spindle organization. During mitosis, SAF-A was localized at the spindles, spindle midzone and cytoplasmic bridge. Depletion of SAF-A by RNA interference induced mitotic delay and defects in chromosome alignment and spindle assembly. We found that SAF-A specifically co-immunoprecipitated with the chromosome peripheral protein nucleolin and the spindle regulators Aurora-A and TPX2, indicating that SAF-A is associated with nucleolin and the Aurora-A-TPX2 complex. SAF-A was colocalized with TPX2 and Aurora-A in spindle poles and MTs. Elimination of TPX2 or Aurora-A from cells abolished the association of SAF-A with the mitotic spindle. Interestingly, SAF-A can bind to MTs and contributes to the targeting of Aurora-A to mitotic spindle MTs. Our finding indicates that SAF-A is a novel spindle regulator that plays an essential role in kinetochore-MT attachment and mitotic spindle organization.
Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan.
Nan
N
Ma
Sachihiro
S
Matsunaga
Akihiro
A
Morimoto
Gyosuke
G
Sakashita
Takeshi
T
Urano
Susumu
S
Uchiyama
Kiichi
K
Fukui
D064127:Aurora Kinases; D018797:Cell Cycle Proteins / Q000378:metabolism; D020090:Chromosome Segregation / Q000502:physiology; D006367:HeLa Cells; D034722:Heterogeneous-Nuclear Ribonucleoprotein U / Q000378:metabolism*; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D034622:RNA Interference; D016601:RNA-Binding Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D000097796:Nucleolin
D064127:Aurora Kinases; D018797:Cell Cycle Proteins; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D016601:RNA-Binding Proteins; D000097796:Nucleolin; C122167:TPX2 protein, human