Biomedical subjects

Liang-Biao Chen

Publications and source records attributed to Liang-Biao Chen.

4 recordsLinked to original sources

PubMed2005

[Comparative analysis of internal repeating segments in proteins of species from the three kingdoms of life].

In 1970's, Ohno proposed that primordial proteins might evolve from periodic amplification of oligopeptides. Internal repeating segments in proteins may play important roles in functional evolution of proteins. In this study,a new method was designed to extract internal repeating segments from proteomes of 8 modern species belong to eukaryota, bacteria and archaea, respectively. The repeating patterns and the frequencies within proteomes of each kingdom were analyzed by matrix plot. Simple repeat segments were found in eukaryotic proteins with high frequencies,but were much lower in bacteria and none in archaea. Further analysis showed that, the biased usage of amino acids in the internal repeating segments was positively related to the frequencies of individual amino acids in the proteome of a given species. The correlation coefficient was up to 0.95 in prokaryota, with the eukaryota to be lower. The high frequency of simple repeat sequences in eukaryotic proteomes, as well as the disparate relationships of amino acid compositions between the internal repeating segments and their haboring eukaryotic proteomes imply that the fast evolution of simple repeat sequences could be one force that generates the high complexity of eukarytic proteomes.

Animals↗

PubMed2005

Evidence for an ancient whole-genome duplication event in rice and other cereals.

Gene duplication has been proposed as an accelerator of evolution. Ancient genome duplication events have been identified in diverse organisms, such as yeast, vertebrates, and Arabidopsis. Here, we have identified a whole genome duplication event (WGD) in the rice genome, which took place prior to the divergence of grasses about 70 million years ago (mya). A total of 117 duplicated blocks were detected, which are distributed on all 12 chromosomes and cover about 60% of the rice genome. About 20% genes on these duplicated segments are retained as duplicate pairs. In contrast, 60% of the transcription factor genes are retained as duplicates. The identification of a WGD in the ancestral grass genome will impact the study of grass genome evolution, and suggest that polyploidization and subsequent gene losses and chromosomal rearrangements have played an important role in the diversification of grasses.

Edible Grain↗

PubMed2005

[Characterization of a multimer type III antifreeze protein gene from the Antarctic eel pout (Lycodichthys dearborni)].

To survive the freezing marine environment, the Antarctic eel pout, Lycodichthys dearborni synthesizes high concentration of type III antifreeze proteins (AFP III). In the process of characterizing the various types of AFP III mRNA present in the L. dearboni liver, a 2.87 kb mRNA encodes for multiple domains of AFP III was identified. This cDNA encodes 12 tandemly repeated segments, each translates into a 7 kD AFP III molecule plus a 9-amino acid linker. This naturally occurred and functional multimer type III antifreeze protein gene is the first of this kind being identified. The organization strongly mimics the polyprotein structure found in the genes for another type of bio-antifreezes, the antifreeze glycoprotein, AFGP. The AFP III and AFGP are compositionally and structurally completely different, and synthesized by fishes in different suborders. The presence of the similar polyprotein structures in the different types of antifreeze genes may imply a common organizational mechanism in the fish genomes for adapting to the extremely cold polar environment.

Amino Acid Sequence↗

PubMed2005

Features of coding and noncoding sequences based on 3-tuple distributions.

The origin of non-coding sequences, especially introns,is an outstanding issue that has been receiving continuous debate for the last two decades. In the current work we use a mathematical model to characterize DNA sequences and find that the 3-tuple distributions in different reading frames of a given coding sequence differ sharply from each other, while they are almost identical to each other in introns or other non-coding sequences. SREs (Symmetric relative entropies) decrease progressively from coding sequences of primitive prokaryotes to those of advanced eukaryotes and from non-coding sequences of low eukaryotes to those of high eukaryotes with a correlation coefficient of 0.86. In silico evolution experiments show that SREs typical of higher eukaryotic introns can be achieved from prokaryotic coding sequences as the mutation ratio reaches 2/100. The fact that (a total of 25 introns) from all three different genomes S. pombe, C. elegans and H. sapiens searched are found to share high sequence identity with coding regions indicates that at least some introns may have come directly from CDS (coding sequences). We suggest that SREs may be a useful feature for evolutionary study.

Algorithms↗