Midkine accumulated in nucleolus of HepG2 cells involved in rRNA transcription.
OBJECTIVE
To investigate the ultrastructural location of midkine (MK) in nucleolus and function corresponding to its location.


METHODS
To investigate the ultrastructural location of MK in nucleolus with immunoelectronic microscopy. To study the role that MK plays in ribosomal biogenesis by real-time PCR. The effect of MK on anti-apoptotic activity of HepG2 cells was studied with FITC-conjugated annexin V and propidium iodide PI double staining through FACS assay.


RESULTS
MK mainly localized in the granular component (GC), dense fibrillar component (DFC) and the border between the DFC and fibrillar center (FC). The production of 45S precursor rRNA level was decreased significantly in the presence of MK antisense oligonucleotide in the HepG2 cells. Furthermore, it was found that exogenous MK could protect HepG2 from apoptosis significantly.


CONCLUSIONS
MK was constitutively translocated to the nucleolus of HepG2 cells, where it accumulated and mostly distributed at DFC, GC components and at the region between FC and DFC, MK played an important role in rRNA transcription, ribosome biogenesis, and cell proliferation in HepG2 cells. MK might serve as a molecular target for therapeutic intervention of human carcinomas.
Dai
Li-Cheng
LC
Huzhou key laboratory of Molecular Medicine, Huzhou Central Hospital, Huzhou 313000, China. dlc@hzhospital.com
Shao
Jian-Zhong
JZ
Min
Li-Shan
LS
Xiao
Yong-Tao
YT
Xiang
Li-Xin
LX
Ma
Zhi-Hong
ZH
D021581:Active Transport, Cell Nucleus; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism* / Q000648:ultrastructure; D049109:Cell Proliferation; D002469:Cell Separation; D005434:Flow Cytometry; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D000078792:Midkine; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012335:RNA, Ribosomal / Q000378:metabolism*; D014158:Transcription, Genetic
C066254:MDK protein, human; D009414:Nerve Growth Factors; D016376:Oligonucleotides, Antisense; D012335:RNA, Ribosomal; C088179:RNA, ribosomal, 45S; D000078792:Midkine