Cloning and characterization of two processed pseudogenes and the cDNA for the murine U1 snRNP-specific protein C |
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| Institution: | 1. Equipment Division, Foshan Nanhai District Health Care Hospital for Women and Children, Nanhai Children''s Hospital, Foshan, China;2. Division of Vascular Surgery, National‐Local Joint Engineering Laboratory of Vascular Disease Treatment, Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, Guangdong Engineering Laboratory of Diagnosis and Treatment of Vascular Disease, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China;3. Department of Cardiology, Guangdong Cardiovascular Institute, Guangdong Provincial Key Laboratory of Coronary Heart Disease Prevention, Guangdong Provincial People''s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China;4. Sun Yat-sen University Cancer Center, Sun Yat-sen University, Guangzhou, China;5. State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University, Guangzhou, China;6. Department of Radiation Oncology, Cancer Center, Sun Yat-sen University, Guangzhou, China;1. Department of Medical Genetics and Division of Human Morbid Genomics, West China Hospital, Sichuan University, Chengdu, China;2. Department of Medical Biology, North Sichuan Medical College, Nanchong, China;1. RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany;2. Department of Physics and Astronomy, University of California, Irvine, USA;3. IMAPP, Radboud University Nijmegen, Nijmegen, Netherlands;4. Nikhef, Science Park, Amsterdam, Netherlands |
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| Abstract: | Genes for the snRNP proteins U1-70K, U1-A, Sm-B′/B, Sm-D1 and Sm-E have been isolated from various metazoan species. The genes for Sm-D1 and Sm-E, which were isolated from a murine and human source respectively, appear to belong to a multigene family. It has been suggested that also for the mammalian U1-C protein such a multigene family exists. With the human U1-C cDNA as a probe, two genes containing sequences homologous to the probe sequence were isolated from a mouse genomic library. Simultaneously, a murine U1-C cDNA was isolated from a mouse cDNA library. This 0.74 kb cDNA contains an open reading frame (ORF) of 477 bp encoding a polypeptide of 159 amino acids (aa) which differs at only one position (position 65) from the human U1-C protein. One of the isolated U1-C genes contains an ORF as well and shares 92% nucleotide sequence identity with the mouse U1-C cDNA. The features of this gene, in particular the absence of introns, the acquisition of a 3′ poly(A) tail and flanking direct repeats, indicate that it represents a processed pseudogene. At the predicted aa sequence level, substitutions of conserved residues at functionally important positions are observed, strongly suggesting that expression of this gene would not lead to a functional polypeptide. The second U1-C gene appeared to be a pseudogene as well because it is also intronless and contains a frameshift mutation compared to the ORF in the mouse U1-C cDNA. The characterization of these two pseudogenes points to the existence of a U1-C multigene family in mice. Furthermore, comparison of aa sequences of the murine, human and Xenopus U1-C shows that the protein is highly conserved through evolution. Since the Xenopus U1-C differs from the two mammalian counterparts solely at a number of positions in the C-terminal region, it can be concluded that aa changes are less well tolerated in the N-terminal region of U1-C than in the rest of the protein. |
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