Aberrant accumulation of PTTG1 induced by a mutated thyroid hormone beta receptor inhibits mitotic progression.
Overexpression of pituitary tumor-transforming 1 (PTTG1) is associated with thyroid cancer. We found elevated PTTG1 levels in the thyroid tumors of a mouse model of follicular thyroid carcinoma (TRbeta(PV/PV) mice). Here we examined the molecular mechanisms underlying elevated PTTG1 levels and the contribution of increased PTTG1 to thyroid carcinogenesis. We showed that PTTG1 was physically associated with thyroid hormone beta receptor (TRbeta) as well as its mutant, designated PV. Concomitant with thyroid hormone-induced (T3-induced) degradation of TRbeta, PTTG1 proteins were degraded by the proteasomal machinery, but no such degradation occurred when PTTG1 was associated with PV. The degradation of PTTG1/TRbeta was activated by the direct interaction of the liganded TRbeta with steroid receptor coactivator 3 (SRC-3), which recruits proteasome activator PA28gamma. PV, which does not bind T3, could not interact directly with SRC-3/PA28gamma to activate proteasome degradation, resulting in elevated PTTG1 levels. The accumulated PTTG1 impeded mitotic progression in cells expressing PV. Our results unveil what we believe to be a novel mechanism by which PTTG1, an oncogene, is regulated by the liganded TRbeta. The loss of this regulatory function in PV led to an aberrant accumulation of PTTG1 disrupting mitotic progression that could contribute to thyroid carcinogenesis.
Ying
Hao
H
Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA.
Furuya
Fumihiko
F
Zhao
Li
L
Araki
Osamu
O
West
Brian L
BL
Hanover
John A
JA
Willingham
Mark C
MC
Cheng
Sheue-Yann
SY
D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008024:Ligands; D051379:Mice; D008822:Mice, Transgenic; D008938:Mitosis; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D064249:Securin; D037042:Thyroid Hormone Receptors beta / Q000235:genetics / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology
D008024:Ligands; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D064249:Securin; D037042:Thyroid Hormone Receptors beta; D046988:Proteasome Endopeptidase Complex