Back to the future?: Can Europe meet its labour needs through temporary migration?

Around 1974, most Western European countries abandoned policies of migrant labour recruitment, and moved towards increasingly restrictive entry rules. Today, employers, politicians and European Commission officials are considering a return to policies of systematic admission of migrant workers. Temporary or seasonal migrant worker programs have already been introduced in a number of countries. This paper inquires whether Europe is likely to return to pre-1974 migrant labour approaches. It examines the demographic, economic and social changes that have led to this new interest in labour immigration, and looks at recent proposals on temporary migration, including those of the Global Commission on International Migration. It discusses experiences of temporary migrant worker programs in Germany and the UK, and goes on to look at the European Commission's 2005 Policy Plan for Legal Migration. The paper shows that the current approaches differ significantly from the guestworker programs of the past and that there is thus no question of a general return to pre-1974 type policies. However, some current approaches do share important common features with past guestworker programs. They may lead to negative social outcomes in both receiving and sending countries

Additional file 1: Figure S1. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

Statistical validation of the AAA domain classification. (A) We used a resampling approach to evaluate the quality of our Hidden Markov Models (HMMs). New models were trained with a random subset of 90 % of the original sequences used to generate each model. We used the other 10 % as the search database with a fixed size of 100,000 sequences. This process was repeated 1000 times and we considered the profile with the best expectation value to be correct. The positive predictive rate (PPR, black, left) and the sensitivity (white, right) are displayed. All models achieved at least 97 % PPR and sensitivity. (B-D) The Cdc48 family is part of a superfamily of classical AAA proteins that also includes proteasome subunits, metalloproteases, meiotic ATPases, and BCS1 [14]. As all our models were trained using Cdc48 AAA domain sequences, non-Cdc48 AAA domain sequences should be a much weaker fit to these models. To evaluate the specificity of our HMMs, we tested the extent to which our models also recognized non-Cdc48 AAA domains. For this, we selected approximately 1800 sequences from the larger family of classical AAA proteins and scanned these sequences with our models. The results are shown as box plots, including the 5 % and 95 % percentiles as whiskers. The plots show the scores (negative logarithm of the expectation value) of our models for the predictions of (B) Cdc48 sequences and (D) non-Cdc48 sequences. We used the different E-value distributions to define the cut-offs for the confidence of our Cdc48 AAA domain predictions. The 5 % percentile of the expectation value distribution in (B) was used as a ‘strict’ cut-off, whereas the 95 % percentile of the expectation value distribution from (D) served as a ‘soft’ cut-off. An overview of the ‘strict’ versus ’soft’ cut-offs for all Cdc48 domain models are displayed in (C). SPAF.d1 is the only model that reveals a lower ‘strict’ than ‘soft’ cut-off. The ‘strict’ cut-off for this model seems especially low, whereas the ‘soft’ cut-off is in a similar range to most other models. Plotting the scores of predictions on Cdc48 sequences for each AAA domain model reveals that most graphs have a logarithmic characteristic, whereas SPAF.d1 follows a linear trend (data not shown). This indicates a higher degree of diversity within this domain. To uphold the quality of our predictions we decided to use the higher ‘soft’ cut-off as the ‘strict’ cut-off for SPAF.d1 as well. (AI 4 mb

Additional file 6: Figure S4. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

A detailed view of the tail helix region of Cdc48. (A) WebLogo representation [119] of the tail region of different Cdc48 family members. Note that the C-terminal HbYX motif of Cdc48 is not maintained in other family members, with the possible exception of Pex1. (B) The structure of the tail region of Cdc48 (PDB: 3CF1 [43]). In the tail helix (in yellow) of Cdc48, the residue Y755 contacts the sensor 1 residue N624. Unfortunately, the structure of the D2 domain of human nuclear VCP-like (NVL, (PDB ID: 2X8A) does not include the tail helix and therefore it cannot be seen whether its tyrosine also interacts with the Sensor 1 asparagine. (AI 5 mb

Additional file 10: Table S4. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

Sequence sources. Data integrated as of 31 December 2015. (DOCX 33 kb

Additional file 2: Table S1. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

Repertoire of the Cdc48 family members in selected species representing the different major eukaryotic lineages. The eight different Cdc48 family members are present in most eukaryotic lineages, suggesting that these proteins were present in the last eukaryotic common ancestor (LECA). A filled black circle indicates the presence of the family member. A filled blue circle denotes that the factor is encoded by the nucleomorph. (DOCX 44 kb

Additional file 4: Table S2. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

List of representative species used to calculate the evolutionary trees of the entire Cdc48 family. (DOCX 44 kb

Additional file 12: Figure S8. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

WebLogo representation of the two D-domains of the different Cdc48 family members. Sequence logos were generated from alignments of the D-domains of different Cdc48 family members from more than 500 eukaryotes using WebLogo software [119] (see Fig. 3). The overall height of a stack indicates the sequence conservation at a certain position, whereas the height of symbols within the stack indicates the relative frequency of each amino acid at that position. (AI 11 mb

Additional file 3: Figure S2. of Shedding light on the expansion and diversification of the Cdc48 protein family during the rise of the eukaryotic cell

Structural elements of the tandem D-domains of Cdc48. The two D-domains of Cdc48 are formed by two subdomains. (A) The N-terminal αβ subdomain contains various motifs like the Walker A motif (P-loop), the Walker B motif, and the polar Sensor 1 residue, which are important for ATP binding and hydrolysis. The conserved arginine residues at the end of α4, referred to as the Arg finger, are in proximity to the γ-phosphate of the bound ATP in the neighboring subunit. Note that the subunits are active only as hexameric assemblies, a key feature of this protein superfamily. The Cdc48 family belongs to the clade of classical AAA proteins that have a small helical insertion before helix α2 within the Rossman fold [14, 15, 18–20, 22]. The C-terminal subdomain is α-helical. A stretch after Helix α7 that was not resolved in the structure is shown as a dashed line. The base of Helix α7 comprises the Sensor 2 region. Both D-domains of Cdc48 possess a conserved GAD motif in this region. The Sensor 2 aspartate of the D1-domain contacts a conserved stretch at the base of the D1-D2 linker and might be important for communication between the two D-domains (Additional file 5: Figure S3). The Sensor 2 aspartate of the D2-domain of Cdc48 interacts with a stretch in front of the C-terminal helix and thus might help to position this helix [43, 45]. The tail helix is followed by a C-terminal extension with a penultimate HbYX motif (Additional file 6: Figure S4). Usually, this motif is flanked by a stretch of three negatively charged residues. In animals, the tyrosine of the HbYX motif can be phosporylated in vivo [120–122]. The extension serves as binding site for other factors and is also thought to help Cdc48 to dock onto the proteasome. The secondary structure elements are shown according to [18]. (B) Structure of the tandem D-domains of Cdc48 (PDB: 3CF1, [43]). Important structure motifs are colored as in (A). (AI 3 mb