Characterization of Endogenous Human Promyelocytic Leukemia Isoforms

Abstract

Promyelocytic leukemia (PML) has been implicated in a variety of functions, including control of TP53 function and modulation of cellular senescence. Sumolated PML is the organizer of mature PML bodies, recruiting a variety of proteins onto these nuclear domains. The PML gene is predicted to encode a variety of protein isoforms. Overexpression of only one of them, PML-IV, promotes senescence in human diploid fibroblasts, whereas PML-III was proposed to specifically interact with the centrosome. We show that all PML isoform proteins are expressed in cell lines or primary cells. Unexpectedly, we found that PML-III, PML-IV, and PML-V are quantitatively minor isoforms compared with PML-I/II and could not confirm the centrosomal targeting of PML-III. Stable expression of each isoform, in a pml-null background, yields distinct subcellular localization patterns, suggesting that, like in other RBCC/TRIM proteins, the COOHterminal domains of PML are involved in interactions with specific cellular components. Only the isoform-specific sequences of PML-I and PML-V are highly conserved between man and mouse. That PML-I contains all conserved exons and is more abundantly expressed than PML-IV suggests that it is a critical contributor to PML function(s). (Cancer Res 2006; 66(12): 6192-8)

Interferon Regulatory Factor-8 Is Indispensable for the Expression of Promyelocytic Leukemia and the Formation of Nuclear Bodies in Myeloid Cells

“…We report here that in U937 cells the expression level of PML-I is mainly elevated in activated cells. This fits with recent a report demonstrating that PML-I protein is much more abundant in macrophages (59). It was recently reported that PML-I forms a complex with AML1, targets it into nuclear bodies, enhances AML1-mediated transcription, and stimulates differentiation of myeloid cells (37).…”

SUMO modification of E1B-55K oncoprotein regulates isoform-specific binding to the tumour suppressor protein PML

“…Although our results indicate a general affinity of E1B-55K for human PML-IV/V as well as a specific subset of rat PML, which may represent the rat orthologs of these isoforms, it seems premature to draw a final conclusion of the exchangeability of results obtained in either of these two systems as no data are available concerning the expression of PML in rats (Supplementary Figure 1). In this context, recent data concerning the organization of the murine pml locus underline the possibility of species-specific PML expression with partial homologous nevertheless considerably differing PML isoforms (Goddard et al, 1995;Condemine et al, 2006). Ongoing studies are dedicated to reveal the molecular background of the isoform-specific E1B-55K PML interaction during infection (Figure 3) as E1B-55K per se only seems to be capable of binding to PML-IV/V (Figure 2).…”

“…As PML expression is frequently deregulated in human tumour cell lines and/ or during oncogenesis Gurrieri et al, 2004;Scaglioni et al, 2006), we analysed several human tumour and pseudoprimary cell lines for endogenous PML expression (Supplementary Figure 1). Consequently, we decided to use human hepatocytic cells (HepaRG) (Gripon et al, 2002;Cerec et al, 2007), as they express PML in the well-defined physiological amounts (Condemine et al, 2006) and represent a suitable system to analyse endogenously PML components during viral infection Lukashchuk and Everett, 2010). Cells were infected with wild-type virus (H5pg4100), E1B-55K null mutant H5pm4149 (Kindsmu¨ller et al, 2009) or previously described H5pm4102/H5pm4101 virus harbouring mutations within the SCM (K104R)/NES (L83/87/91A) of E1B-55K (Kindsmu¨ller et al, 2007).…”

E6AP promotes the degradation of the PML tumor suppressor

“…This antibody was raised against amino acids 1-581 of mouse PML, which is composed of 808 residues and is approximately 90-106 kDa 27 corresponding to mouse isoform 1 (NM 08884), the ortholog of the human isoform I. 28 In the MEF lysates, this antibody recognized the expected B90-106 kDa band and an additional major PML isoform, at B50 kDa. Unlike the well-studied human PML isoforms, however, the identity of additional mouse isoforms is less clear.…”