TMEM155

TMEM155 is located on the minus strand of human chromosome 4 (4q27) and spans 13,611 base pairs.[6]

Cytogenetic band: 4q27[3]

TMEM155 is neighbored by TMEM155 is neighbored on chromosome 4 by CCNA2, a gene encoding for cyclin A2, and ANXA5, which encodes annexin A5.[4] It is also neighbored by PP12613 located on the positive strand.

The gene on chromosome 4 encoding for TMEM155 spans 6,487 nucleotides.[5] This gene spans from base pairs 121,758,930 and 121,765,427 on chromosome 4.[3] The longest variant ofTMEM155 has 5 exons detailed in the table below:[5]

There are 7 isoforms of TMEM155 precursor mRNA.[5] TMEM155 isoform 5 is the longest mRNA and is 2,429 bp long.[3] The shortest isoform is variant 4 and this variant is 2,035 bp long.[5] Isoforms are detailed in the table below.[5]

TMEM155 protein is 130 amino acids in length.[3] The TMEM155 protein in its full form is 14.2 kD in molecular weight with an isoelectric point of 10.29[7] Without its signal peptide it is 11.8 kD.[7] The protein interacts with the membrane once, with one transmembrane domain as seen below.

TMEM155 has a single transmembrane domain through the membrane of the ER.[8]

TMEM155 has a secondary structure composed of 23.5% alpha-helices, 67% beta-sheets, 9.5% turns and coils.[9]

Predicted tertiary structure of TMEM155[10]

The tertiary structure of TMEM155 is predicted in the image on the right. This is predicted to be the structure of the N-terminus tail of TMEM155 located inside the ER membrane.

TMEM155 has sites for O-glycosylation at ser78, thr79, and pro80.[11] It has sites for O-GlcNac at thr79 and ser121[12] It is a target for sumoylation from ile126 to val130.[13] There is a glycation site at lys102.[14]

TMEM155 contains a sequence which functions as an ER retention signal.[15]

TMEM155 interacts with LMBR1 and TMEM259.[16]  LMBR1 is a known lipocalin transmembrane receptor. TMEM259 is another transmembrane protein.

There are several promoters of the TMEM155 gene.[17] The promoter region of the gene is bound by several transcription factors involved in regulating chromatin structure, development, cell cycle, and immune responses.[18] TMEM155 is expressed highly in the brain, placenta, and lymph nodes.[5] Below is a table detailing the transcription factor binding sites for the GXP_319937 promoter of TMEM155.[18] The table below details the transcription factors that bind the promoter region of TMEM155 and the sequences which they bind.

There are 4 splice enhancers of TMEM155.[17] These enhancer sites come on the 5' end of the TMEM155 gene and contain binding sites for transcription factors RCOR1, MILLT1, SIN3A, NFIC, STAT3, JUNB, FOS, EGR1, PHB2, RUNX3, and SRF.[17] Many of these transcription factors are involved with regulation cell growth and tumor suppression.

The upregulation of TMEM155 has been found in basal cell nevus syndrome fibroblasts.[21] TMEM155 was also found to be upregulated in corneal keratinocytes,[22] which could contribute to the upregulation of the gene being associated with nystagmus.

TMEM155 regulation co-varies with families that have instances of essential tremor,[23]

Hypermethylated TMEM155 is a potential biomarker for HER2+ breast cancer.[24] The expression of TMEM155 was found to be higher in the oocytes of women with low antral follicular count, meaning it could be involved in the regulation of female fertility.[25]