Dataset Information

Nucleotide Composition of Human Ig Nontemplated Regions Depends on Trimming of the Flanking Gene Segments, and Terminal Deoxynucleotidyl Transferase Favors Adding Cytosine, Not Guanosine, in Most VDJ Rearrangements.

ABSTRACT: The formation of nontemplated (N) regions during Ig gene rearrangement is a major contributor to Ab diversity. To gain insights into the mechanisms behind this, we studied the nucleotide composition of N regions within 29,962 unique human VHDJH rearrangements and 8728 unique human DJH rearrangements containing exactly one identifiable D gene segment and thus two N regions, N1 and N2. We found a distinct decreasing content of cytosine (C) and increasing content of guanine (G) across each N region, suggesting that N regions are typically generated by concatenation of two 3' overhangs synthesized by addition of nucleoside triphosphates with a preference for dCTP. This challenges the general assumption that the terminal deoxynucleotidyl transferase favors dGTP in vivo. Furthermore, we found that the G and C gradients depended strongly on whether the germline gene segments were trimmed or not. Our data show that C-enriched N addition preferentially happens at trimmed 3' ends of VH, D, and JH gene segments, indicating a dependency of the transferase mechanism upon the nuclease mechanism.

SUBMITTER: Funck T

PROVIDER: S-EPMC6121214 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Nucleotide Composition of Human Ig Nontemplated Regions Depends on Trimming of the Flanking Gene Segments, and Terminal Deoxynucleotidyl Transferase Favors Adding Cytosine, Not Guanosine, in Most VDJ Rearrangements.

Funck Tina T Barnkob Mike Bogetofte MB Holm Nanna N Ohm-Laursen Line L Mehlum Camilla Slot CS Möller Sören S Barington Torben T

Journal of immunology (Baltimore, Md. : 1950) 20180810 6

The formation of nontemplated (N) regions during Ig gene rearrangement is a major contributor to Ab diversity. To gain insights into the mechanisms behind this, we studied the nucleotide composition of N regions within 29,962 unique human VHDJH rearrangements and 8728 unique human DJH rearrangements containing exactly one identifiable D gene segment and thus two N regions, N1 and N2. We found a distinct decreasing content of cytosine (C) and increasing content of ...[more]

PMID: 30097530

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Project description:Hepatitis delta virus (HDV) is a significant human pathogen that causes acute and chronic liver disease; there is no licensed therapy. HDV is a circular negative-sense single-stranded RNA (ssRNA) virus that produces three RNAs in infected cells, genome, antigenome, and mRNA; the latter encodes hepatitis delta antigen (HDAg), the viral protein. These RNAs are synthesized by host DNA-dependent RNA polymerase acting as an RNA-dependent RNA polymerase. Although HDV genome RNA accumulates to high levels in infected cells, the mechanism by which this process occurs remains poorly understood. For example, the nature of the 5' end of the genome, including the synthesis start site and its chemical composition, is not known. Analysis of this process has been challenging because the initiation site is part of an unstable precursor in the rolling-circle mechanism by which HDV genome RNA is synthesized. In this study, circular HDV antigenome RNAs synthesized in vitro were used to directly initiate HDV genome RNA synthesis in transfected cells, thus enabling the detection of the 5' end of the genome RNA. The 5' end of this RNA is capped, as expected for a polymerase II product. Initiation begins at position 1646 on the genome, which is located near the loop end proximal to the start site for HDAg mRNA synthesis. Unexpectedly, synthesis begins with a guanosine that is not conventionally templated by the HDV RNA. IMPORTANCE Hepatitis delta virus (HDV) is a unique virus that causes severe liver disease. It uses host RNA polymerase II to copy its circular RNA genome in a unique and poorly understood process. Although the virus RNA accumulates to high levels within infected cells, it is not known how the synthesis of the viral RNA begins or even where on the genome synthesis starts. Here, we identify the start site for the initiation of HDV genome RNA synthesis as position 1646, which is at one end of the closed-hairpin-like structure of the viral RNA. The 5' end of the RNA is capped, as expected for polymerase II products. However, RNA synthesis begins with a guanosine that is not present in the genome. Thus, although HDV uses polymerase II to synthesize the viral genome, some details of the initiation process are different. These differences could be important for successfully targeting virus replication.

Dataset Information

Nucleotide Composition of Human Ig Nontemplated Regions Depends on Trimming of the Flanking Gene Segments, and Terminal Deoxynucleotidyl Transferase Favors Adding Cytosine, Not Guanosine, in Most VDJ Rearrangements.

Publications

Nucleotide Composition of Human Ig Nontemplated Regions Depends on Trimming of the Flanking Gene Segments, and Terminal Deoxynucleotidyl Transferase Favors Adding Cytosine, Not Guanosine, in Most VDJ Rearrangements.

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