Role of the conserved AAUAAA sequence: four AAUAAA point mutants prevent messenger RNA 3' end formation

Sequences required for 3' end formation of human U2 small nuclear RNA

Xenopus oocytes injected with human U2 snRNA genes synthesize mature U2 as well as a U2 precursor with about 10 extra 3' nucleotides (human pre-U2 RNA). Formation of the pre-U2 3' end requires a downstream element located between position +16 and +37 in the U2 3'-flanking sequence. The distance between this element and the U2 coding region can be increased without affecting formation of the pre-U2 3' end. When the natural sequence surrounding the pre-U2 3' end is changed, novel 3' ends are still generated within a narrow range upstream from the element. The 3' terminal stem-loop of U2 snRNA is not required for pre-U2 3' end formation. A sequence within the 3' element (GTTTN0-3AAAPuNNAGA) is conserved among snRNA genes transcribed by RNA polymerase II. Our results suggest that the 3' ends of pre-U2 RNA and histone mRNA may be generated by related but distinct RNA processing mechanisms.

Nucleotide sequence of transforming human c-sis cDNA clones with homology to platelet-derived growth factor

Three c-sis cDNA clones were obtained from polyadenylated RNA of a human T-cell lymphotropic virus (HTLV) type I transformed cell line. Two clones, designated pSM-1 and pSM-2, have cDNA inserts of 2498 and 2509 base pairs (bp), respectively, excluding the sizes of the guanylate tails, and the polyadenylate tracts. These clones are shorter than the estimated size of the c-sis mRNA of 4200 bp. Both of these clones can transform NIH 3T3 cells. The third clone, designated pSM-3 has a cDNA insert of 1421 bp and lacks transforming activity. The sequence of clone pSM-1 reveals a single long open reading frame (nucleotides 118-840) encoding chain A of platelet-derived growth factor, and two segments with homology to v-sis (nucleotides 182-871 and 1021-1325). Sequence homology is noted in the 3' untranslated region to the corresponding regions of the beta 1 interferon (IFN), human and murine beta-nerve growth factor (NGF), human interleukin 2 (IL2) genes, and tubulin pseudogenes. However, no typical AATAAA polyadenylation signal is present. An alternating (dCdA)n X (dGdT)n sequence is present in the 3' flanking cellular sequences similar to those in the corresponding position of the human proenkephalin gene, in the first intron of the gamma-IFN gene, and the second intron of the beta-NGF gene.

Accurate cleavage and polyadenylation of exogenous RNA substrate

Purified precursor RNA containing the L3 polyadenylation site of late adenovirus 2 mRNA is accurately cleaved and polyadenylated when incubated with nuclear extract from HeLa cells. The reaction is very efficient; 75% of the precursor is correctly processed. Cleavage is rapidly followed by polymerization of an initial poly(A) tract of approximately 130 nucleotides. Additional adenosine residues are added during further incubation. In the presence of the ATP analog alpha-beta-methylene-adenosine 5' triphosphate, the precursor RNA is cleaved but not polyadenylated, suggesting that processing is not coupled to the synthesis of the initial poly(A) tract. In the absence of free Mg2+, a small RNA of approximately 46 nucleotides is stabilized against degradation. Fingerprint analysis suggests this RNA is produced by endonucleolytic cleavage at the L3 site. Like the in vitro splicing reaction, the in vitro polyadenylation reaction is inhibited by adding antiserum against the small nuclear ribonucleoprotein particle containing U1 RNA.

Formation of the 3' end of U1 snRNA is directed by a conserved sequence located downstream of the coding region

U1 is a small non-polyadenylated nuclear RNA that is transcribed by RNA polymerase II and is known to play a role in mRNA splicing. The mature 3' end of U1 snRNA is formed in at least two steps. The first step generates precursors of U1 RNA with a few extra nucleotides at the 3' end; in the second step, these precursors are shortened to mature U1 RNA. Here, I have determined the sequences required for the first step. Human U1 genes with various deletions and substitutions near the 3' end of the coding region were constructed and introduced into HeLa cells by DNA transfection. The structure of the RNA synthesized during transient expression of the exogenous U1 gene was analyzed by S1 mapping. The results show that a 13 nucleotide sequence located downstream from the U1 coding region and conserved among U1, U2 and U3 genes of different species is the only sequence required to direct the first step in the formation of the 3' end of U1 snRNA.

Cloning, sequence and expression of two distinct human interleukin-1 complementary DNAs

Two distinct but distantly related complementary DNAs encoding proteins sharing human interleukin-1 (IL-1) activity (termed IL-1 alpha and IL-1 beta), were isolated from a macrophage cDNA library. The primary translation products of the genes are 271 and 269 amino acids long, although expression in Escherichia coli of the carboxy-terminal 159 and 153 amino acids produces IL-1 biological activity.

A sequence downstream of A-A-U-A-A-A is required for formation of simian virus 40 late mRNA 3' termini in frog oocytes

The 3' terminus of simian virus 40 late mRNA is formed by nucleolytic cleavage of an mRNA precursor. In this report we show that efficient cleavage requires a sequence in the 3' flanking region, "downstream" of the highly conserved A-A-U-A-A-A sequence. This sequence is not required for polyadenylylation itself or for accurately positioning the 3' terminus that is formed.

Alternative splicing patterns in an aberrantly rearranged immunoglobulin kappa-light-chain gene

Using a 15-nucleotide primer specific for the immunoglobulin kappa-chain gene, we synthesized cDNA from the mRNA of an anti-alpha(1----6)dextran hybridoma. The hybridoma had been produced using MPC-11 as the parental myeloma. Hybridization and sequence analysis of one clone showed that it was derived from a 1.2-kilobase (kb) kappa-chain mRNA that lacked a joining minigene segment (J). The mRNA had the leader region correctly spliced to the variable region (V) but, in the absence of a J, V kappa was flanked by 62 nucleotides (3202-3263) from the intervening sequence (between J5 and the kappa-chain constant region gene C kappa) before being spliced to C kappa. This mRNA originated from the kappa-chain-fragment gene of MPC-11 but differed from the previously described 0.8-kb kappa-chain-fragment mRNA [Choi, E., Kuehl, W.M. & Wall, R. (1980) Nature (London) 286, 776-779; Seidman, J.G. & Leder, P. (1980) Nature (London) 286, 779-783] in which the leader sequence is spliced directly to C kappa. This 1.2-kb mRNA was present as a polyadenylylated species in total cellular RNA but could not be detected in cytoplasmic RNA. Thus, it either failed to be transported out of the nucleus or was rapidly degraded in the cytoplasm. These studies show that transcripts of the kappa-chain-fragment gene are processed by two distinct splicing pathways to yield either a 0.8-kb mRNA with the leader region spliced directly to C kappa or a 1.2-kb mRNA with leader, V, 62 nucleotides of the intervening sequence, and C kappa.