Since the advent of whole-genome sequencing, transposable elements (TEs), just thought to be 'junk' DNA, have been noticed because of their numerous copies in various eukaryotic genomes. Many studies about TEs have been conducted to discover their functions in their host genomes. Based on the results of those studies, it has been generally accepted that they have a function to cause genomic and genetic variations. However, their infinite functions are not fully elucidated. Through various mechanisms, including de novo TE insertions, TE insertion-mediated deletions, and recombination events, they manipulate their host genomes. In this review, we focus on Alu, L1, human endogenous retrovirus, and short interspersed element/variable number of tandem repeats/Alu (SVA) elements and discuss how they have affected primate genomes, especially the human and chimpanzee genomes, since their divergence.
Alu Elements ; Coat Protein Complex I ; DNA ; DNA Transposable Elements ; Endogenous Retroviruses ; Genetic Variation ; Genome ; Humans ; Long Interspersed Nucleotide Elements ; Pan troglodytes ; Primates ; Recombination, Genetic ; Tromethamine

X-linked agammaglobulinemia (XLA) is characterized by early onset of recurrent bacterial infection, markedly reduced levels of all major classes of immunoglobulins in the serum and few mature B cells in the blood. XLA is known to be associated with mutations in Bruton's tyrosin kinase (Btk). The Btk protein consists of 5 functional domains; the pleckstrin homology (PH) domain, the Tec homology (TH) domain, the Src homology 3 (SH3) domain, the SH2 domain, and the kinase (SH1) domain. Mutations in all domains of the Btk gene have been shown to cause XLA. The large number of Alu elements within the human genome provides abundant opportunities for unequal homologous recombination events between Alu repeats, resulting in human disease. We present a case of XLA with deletion of introns 15-18 of Btk gene which were mediated by an Alu-Alu recombination event.
Agammaglobulinemia* ; Alu Elements ; B-Lymphocytes ; Bacterial Infections ; Genome, Human ; Homologous Recombination ; Humans ; Immunoglobulins ; Introns* ; Phosphotransferases ; Recombination, Genetic* ; src Homology Domains

X-linked agammaglobulinemia (XLA) is characterized by early onset of recurrent bacterial infection, markedly reduced levels of all major classes of immunoglobulins in the serum and few mature B cells in the blood. XLA is known to be associated with mutations in Bruton's tyrosin kinase (Btk). The Btk protein consists of 5 functional domains; the pleckstrin homology (PH) domain, the Tec homology (TH) domain, the Src homology 3 (SH3) domain, the SH2 domain, and the kinase (SH1) domain. Mutations in all domains of the Btk gene have been shown to cause XLA. The large number of Alu elements within the human genome provides abundant opportunities for unequal homologous recombination events between Alu repeats, resulting in human disease. We present a case of XLA with deletion of introns 15-18 of Btk gene which were mediated by an Alu-Alu recombination event.
Agammaglobulinemia* ; Alu Elements ; B-Lymphocytes ; Bacterial Infections ; Genome, Human ; Homologous Recombination ; Humans ; Immunoglobulins ; Introns* ; Phosphotransferases ; Recombination, Genetic* ; src Homology Domains

Even though it represents 6 13% of human genomic DNA, Alu sequences are rarely found in coding regions. When in exon region, over 80 % of them are found in 3' untranslated region (UTR). Pseudogenes are an important component of human genome. Their functions are not clearly known and the mechanism of how they are generated is still debatable. Both the Alu and Pseudogenes are important research problems in molecular biology. mRNA is thought to be a prime source of pseudogene and active research is going on its molecular mechanism. We report, for the first time, that mRNAs containing Alu repeats at 3' UTR has a significantly high correlation with processed pseudogenes, suggesting a possibility that Alu containing mRNAs have a high tendency to become processed pseudogenes. It is known that about 10% of all human genes have been transposed. Transposed genes at 3' UTR without Alu repeat have about two processed pseudogenes per gene on average while we found with statistical significance that a transposed gene with Alu had over three processed Pseudogenes on average. Therefore, we propose Alu repeats as a new and important factor in the generation of pseudogenes.
3' Untranslated Regions* ; Alu Elements* ; Clinical Coding ; DNA ; Exons ; Genome, Human ; Humans ; Molecular Biology ; Pseudogenes* ; RNA, Messenger*

The aim of this study is to identify hRad21-binding sites in human chromosome, the core component of cohesin complex that held sister chromatids together. After chromatin immunoprecipitation with an hRad21 antibody, it was cloned the recovered DNA and sequenced 30 independent clones. Among them, 20 clones (67%) contained repetitive elements including short interspersed transposable elements (SINE or Alu elements), long terminal repeat (LTR) and long interspersed transposable elements (LINE), fourteen of these twenty (70%) repeats clones had Alu elements, which could be categorized as the old and the young Alu Subfamily, eleven of the fourteen (73%) Alu elements belonged to the old Alu Subfamily, and only three Alu elements were categorized as young Alu subfamily. There is no CpG island within these selected clones. Association of hRad21 with Alu was confirmed by chromatin immunoprecipitation-PCR using conserved Alu primers. The primers were designed in the flanking region of Alu, and the specific Alu element was shown in the selected clone. From these experiments, it was demonstrated that hRad21 could bind to SINE, LTRs, and LINE as well as Alu.
Alu Elements ; Chromatids ; Chromatin ; Chromatin Immunoprecipitation ; Chromosomes, Human* ; Clone Cells ; CpG Islands ; DNA ; DNA Transposable Elements ; Humans ; Humans* ; Siblings ; Terminal Repeat Sequences

Transposable elements are one of major sources to cause genomic instability through various mechanisms including de novo insertion, insertion-mediated genomic deletion, and recombination-associated genomic deletion. Among them is Alu element which is the most abundant element, composing ~10% of the human genome. The element emerged in the primate genome 65 million years ago and has since propagated successfully in the human and non-human primate genomes. Alu element is a non-autonomous retrotransposon and therefore retrotransposed using L1-enzyme machinery. The 'master gene' model has been generally accepted to explain Alu element amplification in primate genomes. According to the model, different subfamilies of Alu elements are created by mutations on the master gene and most Alu elements are amplified from the hyperactive master genes. Alu element is frequently involved in genomic rearrangements in the human genome due to its abundance and sequence identity between them. The genomic rearrangements caused by Alu elements could lead to genetic disorders such as hereditary disease, blood disorder, and neurological disorder. In fact, Alu elements are associated with approximately 0.1% of human genetic disorders. The first part of this review discusses mechanisms of Alu amplification and diversity among different Alu subfamilies. The second part discusses the particular role of Alu elements in generating genomic rearrangements as well as human genetic disorders.
Alu Elements* ; DNA Transposable Elements ; Genetic Diseases, Inborn ; Genome ; Genome, Human ; Genomic Instability ; Humans* ; Nervous System Diseases ; Primates ; Recombination, Genetic ; Retroelements

OBJECTIVETo investigate the frequencies of HLA-Alu repeat polymorphisms (AluMICB, AluTF, AluHJ, AluHG and AluHF) in Chinese Lisu and Nu ethnic populations.

METHODSThe frequencies of HLA-Alu repeat polymorphisms in above populations were determined with polymerase chain reaction (PCR). The associations between HLA-Alu repeat polymorphisms and HLA-A, HLA-B and HLA-C alleles were also analyzed. Phylogenetic trees were constructed with genetic distance calculated from the frequencies of HLA-Alu repeat polymorphisms.

RESULTSFrequencies of AluTF*2 and AluHF*2 were different between the two populations (P< 0.05), while those of other three insertions were similar. The strength of association between HLA-Alus and HLA alleles were different (P< 0.05) in the two populations. Although AluMICB*2 were associated with HLA-B*56:01 in both populations, the association was stronger in Lisu population (74.0%) but moderate in Nu population (30.7%). HLA-Alus were associated with particular HLA subtypes, e.g., AluHG*2 with certain HLA-A*02 subtypes. By phylogenetic analysis, Lisu and Nu were clustered together with southern Chinese and Thai populations.

CONCLUSIONThe distribution of HLA-Alus and the strength of associations between HLA-Alus and HLA class I alleles have varied between the two populations. Study of this association may facilitate identification of origins, evolution, progenitor haplotypes and recombination within the HLA class I region.

Adolescent ; Adult ; Aged ; Alleles ; Alu Elements ; Asian Continental Ancestry Group ; genetics ; Child ; Female ; Genes, MHC Class I ; Humans ; Male ; Middle Aged ; Phylogeny ; Polymorphism, Genetic ; Young Adult

OBJECTIVETo investigate the polymorphism of DYS287 among 28 ethnic populations in 9 provinces of China.

METHODYAP element was detected by Touchdown PCR amplification and 2% agarose gel electrophoresis.

RESULTSYAP+ frequencies in these ethnic populations were as follows: Zang 36.7%, Tu 23.8%, Yi 18.4%, Pumi 11.3%, Tajik 7.4%, Bai 6.7%, Jino 5.1%, Shandong Han 4%, Mulao 2.7%, and Maonan 1.3%. The rest ethnic populations in our study, including Gansu Han, Yunnan Han, Zhuangzu, Daizu, Lizu, Nuzu, Lisu, Naxi, Lahu, Dulong, Hani, Shezu, Weiwuer, Sala, Kerkizi, Dongxiang, Vazu, and Korea didn't carry YAP + element.

CONCLUSIONSZangzu, Tuzu, Yizu, Pumi, Jino, and Baizu, which belong to Sino-Tibetan language family, carry a high YAP + frequency. Sala, Tuzu, and Tajik, regarded as Central Asia by origin in history and linguistics, also have a high YAP + frequency. Mulao and Maonan, which origin from "Baiyue" ancient ethnic groups, also have a considerable YAP + frequency.

Alu Elements ; genetics ; Asian Continental Ancestry Group ; genetics ; China ; ethnology ; Chromosomes, Human, Y ; genetics ; Electrophoresis, Agar Gel ; Gene Frequency ; Humans ; Male ; Polymerase Chain Reaction ; Polymorphism, Genetic

We exploited the serial analysis of gene expression (SAGE) libraries and human genome database in silico to correlate the breadth of expression (BOE; housekeep-ing versus tissue-specific genes) and peak rate of expression (PRE; high versus low expressed genes) with the density distribution of the retroelements. The BOE status is linearly associated with the density of the sense Alus along the 100 kb nucleotides region upstream of a gene, whereas the PRE status is inversely correlated with the density of antisense L1s within a gene and in the up- and downstream regions of the 0-10 kb nucleotides. The radial distance of intranuclear position, which is known to serve as the global domain for transcription regulation, is reciprocally correlated with the fractions of Alu (toward the nuclear center) and L1 (toward the nuclear edge) elements in each chromosome. We propose that the BOE and PRE statuses are related to the reciprocal distribution of Alu and L1 elements that formulate local and global expression domains.
Alu Elements/*genetics ; Chromosome Mapping/*methods ; Comparative Study ; Databases, Genetic ; Gene Expression Profiling/*methods ; Gene Expression Regulation/*genetics ; Genome, Human ; Humans ; Long Interspersed Nucleotide Elements/*genetics ; Retroelements/genetics ; Sequence Analysis, DNA/*methods ; Statistics ; Tissue Distribution

Transitional-CpG methylation between unmethylated promoters and nearby methylated retroelements plays a role in the establishment of tissue-specific transcription. This study examined whether chromosomal losses reducing the active genes in cancers can change transitional-CpG methylation and the transcription activity in a cancer-type-dependent manner. The transitional-CpG sites at the CpG-island margins of nine genes and the non-island-CpG sites round the transcription start sites of six genes lacking CpG islands were examined by methylation-specific polymerase chain reaction (PCR) analysis. The number of active genes in normal and cancerous tissues of the stomach, colon, breast, and nasopharynx were analyzed using the public data in silico. The CpG-island margins and non-island CpG sites tended to be hypermethylated and hypomethylated in all cancer types, respectively. The CpG-island margins were hypermethylated and a low number of genes were active in the normal stomach compared with other normal tissues. In gastric cancers, the CpG-island margins and non-island-CpG sites were hypomethylated in association with high-level chromosomal losses, and the number of active genes increased. Colon, breast, and nasopharyngeal cancers showed no significant association between the chromosomal losses and methylation changes. These findings suggest that chromosomal losses in gastric cancers are associated with the hypomethylation of the gene-control regions and the increased number of active genes.
Alu Elements/genetics ; *Chromosome Deletion ; CpG Islands/*genetics ; *DNA Methylation ; DNA, Neoplasm/chemistry/isolation & purification ; Gene Expression Profiling ; *Genes, Neoplasm ; Humans ; Long Interspersed Nucleotide Elements/genetics ; Polymerase Chain Reaction ; *Promoter Regions, Genetic ; Stomach Neoplasms/*genetics