TMEM8 - a non-globin gene entrapped in the globin web.

For more than 30 years it was believed that globin gene domains included only genes encoding globin chains. Here we show that in chickens, the domain of alpha-globin genes also harbor the non-globin gene TMEM8. It was relocated to the vicinity of the alpha-globin cluster due to inversion of an approximately 170-kb genomic fragment.

The upstream area of the chicken alpha-globin gene domain is transcribed in both directions in the same cells.

It was demonstrated previously that in erythroid chicken cells an extended upstream area of the alpha-globin gene domain is transcribed in both directions as a part of ggPRX gene and a part of a full domain transcript of the alpha-globin gene domain. Here, we show that both DNA chains of the above-mentioned region are transcribed in the same cells and that the corresponding transcripts coexist in nuclei. The data obtained suggest that cells possess a molecular mechanism which in some cases prevents the formation of dsRNA and subsequent destruction of both transcripts in spite of the presence of complementary RNA chains in the cell nucleus.

RNA-dependent nuclear matrix contains a 33 kb globin full domain transcript as well as prosomes but no 26S proteasomes.

Previously, we have shown that in murine myoblasts prosomes are constituents of the nuclear matrix; a major part of the latter was found to be RNase sensitive. Here, we further define the RNA-dependent matrix in avian erythroblastosis virus (AEV) transformed erythroid cells in relation to its structure, presence of specific RNA, prosomes and/or proteasomes. These cells transcribe but do not express globin genes prior to induction.

The 33 kb transcript of the chicken alpha-globin gene domain is part of the nuclear matrix.

Giant nuclear transcripts, and in particular the RNAs of the globin gene domains which are much larger than their canonical pre-mRNAs, have been an enigma for many years. We show here that in avian erythroblastosis virus (AEV)-transformed chicken erythroleukaemic cells, where globin gene expression is abortive, the whole domain of alpha-globin genes is transcribed for about 33 kb in the globin direction and that this RNA is part of the nuclear matrix. Northern blot hybridisation with strand-specific riboprobes, recognising genes and intergenic sequences, and RT-PCR with downstream primers, show that the continuous full domain transcript (FDT) starts in the vicinity of a putative LCR and includes all the genes as well as known regulatory sites, the replication origin, and the DNA loop anchorage region in the upstream area.