Effects of the Bowen-Conradi syndrome mutation in EMG1 on its nuclear import, stability and nucleolar recruitment
HUMAN MOLECULAR GENETICS
Authors: Warda, Ahmed S.; Freytag, Bernard; Haag, Sara; Sloan, Katherine E.; Goerlich, Dirk; Bohnsack, Markus T.
Abstract
Bowen-Conradi syndrome (BCS) is a severe genetic disorder that is characterised by various developmental abnormalities, bone marrow failure and early infant death. This disease is caused by a single mutation leading to the aspartate 86 to glycine (D86G) exchange in the essential nucleolar RNA methyltransferase EMG1. EMG1 is required for the synthesis of the small ribosomal subunit and is involved in modification of the 18S ribosomal RNA. Here, we identify the pre-ribosomal factors NOP14, NOC4L and UTP14A as members of a nucleolar subcomplex that contains EMG1 and is required for its recruitment to nucleoli. The BCS mutation in EMG1 leads to reduced nucleolar localisation, accumulation of EMG1(D86G) in nuclear foci and its proteasome-dependent degradation. We further show that EMG1 can be imported into the nucleus by the importins (Imp) Imp alpha/beta or Imp beta/7. Interestingly, in addition to its role in nuclear import, binding of the Imp beta/7 heterodimer can prevent unspecific aggregation of both EMG1 and EMG1(D86G) on RNAs in vitro, indicating that the importins act as chaperones by binding to basic regions of the RNA methyltransferase. Our findings further indicate that in BCS, nuclear disassembly of the import complex and release of EMG1(D86G) lead to its nuclear aggregation and degradation, resulting in the reduced nucleolar recruitment of the RNA methyltransferase and defects in the biogenesis of the small ribosomal subunit.
U three protein 14a (UTP14A) promotes tumour proliferation and metastasis via the PERK/eIF2a/GRP78 signalling pathway in oesophageal squamous cell carcinoma
JOURNAL OF CANCER
Authors: Li, Kun-Kun; Mao, Cheng-Yi; Ma, Qiang; Bao, Tao; Wang, Ying-Jian; Guo, Wei; Zhao, Xiao-Long
Abstract
Metastasis and malignant proliferation are major obstacles to the treatment of oesophageal squamous cell carcinoma (ESCC), and UTP14A is associated with poor prognosis in ESCC. However, its mechanisms have not been fully elucidated. The TCGA and GEO databases were used to identify candidate target genes and possible downstream targets. Then, the effects were determined in vitro and in vivo through knockdown and overexpression techniques, and the mechanism was explored. UTP14A was significantly higher in the tumour tissue of ESCC patients than in normal tissue. Knockdown of UTP14A significantly suppressed the migration and proliferation of ESCC cells. The PERK/eIF2a signalling pathway was positively regulated by UTP14A, and its tumour-promoting effect was further activated by overexpression of UTP14A. In conclusion, UTP14A might promote the proliferation and metastasis of ESCC cells by inducing PERK/eIF2a signalling pathway expression.