Sigma region located between C, and C, genes of human immunoglobulin heavy chain: possible involvement of tRNA-like structure in RNA splicing

Abstract

Noncoding regions within the cluster of immunoglobulin heavy chain constant genes in the human genome contained a number of repeats. In the mu-delta intron, two repeating units were contained. One 442-base-long fragment located JH-mu intron (defined as "sigma mu(sigma mu)") occupied the position in the mu-delta intron. The other 1166-base-long fragment located somewhere in front of S (class switch) region of C gamma gene was also found in the mu-delta intron. We defined the repeats in the mu-delta intron as "SIGMA (sigma)". The polarities of the longer repeats in the genome were opposite between the mu-delta intron and the upstreams of C gamma genes. These inverted copies (defined as sigma gamma 3 and sigma gamma 4), located 6 kb upstream of their respective C gamma's, were apparently transcribed in vitro, via RNA polymerase III and transcripts should have contained tRNA-like structures. Small DNA fragments capable of encoding tRNA-like structures were also found in corresponding regions of mouse Ig C gamma cluster.

Human interleukin 2 receptor beta-chain gene: chromosomal localization and identification of 5' regulatory sequences.

“…This may have implications for the means ofregulation ofexpression of IL-2Rp. In addition to the d(GT)" repeat, GenBank searches revealed two matches: (i) an 86% homology between -755 and -657 of IL-2Rj3 and sequences contained in the 3' untranslated region of the class II enzyme of human liver alcohol dehydrogenase ir subunit mRNA (38) and (ii) a 75% homology between -722 and -618 of IL-2R/3 and 5' flanking sequences of the o-y3 region that is contained within the human immunoglobulin heavy chain constant region gene cluster (39). Although the extent of these overlapping homologies is highly significant, the function of this sequence is unclear and will require further studies.…”

Non-coding Class Switch Recombination-related transcription in human normal and pathological immune responses

“…A transcriptionally active 309 base-pair (bp) region within the IGHM-IGHD intron was identified (referred hereafter as I δ ) and was included for further analysis (Figure 1B). This region is homologous to Iμ, overlaps with a previously described repeat termed Σμ implicated in μ-δ CSR in IgD + myelomas [22, 23]. For the IGHA1 gene, we identified two potential I H exons (I α1.1 and I α1 .…”

“…[44] is shown in orange. The blue asterisks indicate Hind III sites [22, 23, 43]. C ) Transcriptional landscape of the IGHA1 locus displaying coverage graphs of the IGHA1 , GenCode V24 annotation (green track) , tonsilar naive (SRR834982, blue) and peripheral blood B cells (SRR2097501, red).…”

“…A novel transcribed element (I δ ) located in the IGHM-IGHD intergenic region was identified, which overlaps with a previously described repeat Σ μ region, downstream of an atypical switch region (σδ) involved in non-classical CSR to IgD in mice [42] and humans [43-45]. The Σμ region was originally described as mediator of μ–δ CSR by homologous recombination in myeloma cell lines [22, 23]. The biological role of Σμ is uncertain, because IgD+ EBV-transformed cell lines and human tonsillar B cells undergo μ–δ CSR by non-homologous recombination using σ8 as acceptor switch region [43, 45], in an AID-dependent fashion [44].…”

Presence of immunoglobulin (Ig) M and IgG double isotype-bearing cells and defect of switch recombination in hyper IgM immunodeficiency.

“…Probes JH, 5'-S,,, and S, were prepared from the already published clones (15). Conditions of hybridizations were the same as described (16).…”